B. SUDERSHAN REDDY, J. ( 1 ) THE subject matter that arises for consideration in both these writ petitions is one and the same and, therefore, they can conveniently be disposed of by a common order. The petitioners herein invoked the jurisdiction of the Andhra Pradesh Administrative Tribunal at Hyderabad challenging the constitutional validity of the amended proviso to Rule 6 of the Andhra Pradesh Treasury and Accounts Subordinate Service Rules on various grounds in O. A. Nos. 5312 of 1996 and 383 of 1996 respectively. The Tribunal by its common Judgment dated 13/08/1997 disposed of O. A. No. 6456 of 1995 and Batch, including the above Original Applications, upholding the constitutional validity of the said amended proviso to Rule 6 of the said Rules. The Tribunal after an elaborate consideration of the matter rejected the contentions raised by the petitioners. Hence these writ petitions. ( 2 ) BEFORE adverting to the question as to whether the Tribunal has committed any error in upholding the constitutional validity of the amended proviso to Rule 6 of the Rules, it may be necessary to briefly notice the relevant facts leading to filing of these writ petitions. ( 3 ) THE petitioners in both the writ petitions, at the time of filing of the writ petitions, have been working as Senior Accountants in the Treasuries and Accounts Department, Government of Andhra Pradesh. Their service conditions including the appointment, promotion, seniority etc. , in the Treasuries and Accounts Department are regulated by the rules known as "andhra Pradesh Treasury and Accounts Subordinate Service Rules" (for short the Rules ) made by the Governor in exercise of the powers conferred by the proviso to Article 309 of the Constitution of India. They are the special rules. The rules deemed to have come into force on and with effect from 1-4-1958. According to the said Rules, the promotion from the cadre of Senior Accountant to that of the Superintendent/sub-Treasury Officer is based upon the seniority alone. ( 4 ) THE Government of Andhra Pradesh having carefully examined the proposals of the Director of Treasuries and Accounts about the need for improving the knowledge and skills among the personnel of Treasuries and Accounts Gazetted and Subordinate Services decided to introduce "treasuries and Accounts Service Examination" and accordingly notified its policy decision in G. O. Ms. No. 316, Finance and Planning (F. W.-Admn. No. 316, Finance and Planning (F. W.-Admn. I) Department, dated 14/12/1988 prescribing the qualification of a pass in the said Examination i. e. Treasuries and Accounts Service Examination, Part-I and II to be conducted by the Andhra Pradesh Public Service Commission for promotion of Senior Accountants to the next higher post i. e. Sub-Treasury Officer. Accordingly, a new examination named as "treasures and Accounts Service Examination" consisting of Part-I and II (for short the said examination ) has been introduced. The said G. O. has laid down the criteria for conducting the examination including the syllabus. Only such of those who pass the said examination were made eligible for promotions to the next higher post. ( 5 ) THE Andhra Pradesh Public Service Commission conducted the said examination from November, 1989 and continued to conduct the same every year. The petitioners appeared for the said examination and passed the same along with certain other Senior Accountants in the Department. The petitioners were accordingly expecting the promotions based upon the newly acquired qualification of having passed the said examination conducted by the Andhra Pradesh Public Service Commission. ( 6 ) THE Government of Andhra Pradesh by its subsequent G. O. Ms. No. 154, Finance and Planning (FW. ADMN. I) Department, dated 11-4-1991, having considered the representation of the Andhra Pradesh Treasury Subordinate Service Association, Hyderabad and in view of the difficulties faced by the employees, modified the scheme of Treasuries and Accounts Service Examination introduced in G. O. Ms. No. 316, dated 14-12-1988 and accordingly allowed the examination with books. A special provision was made in the said G. O. , to the effect that the employees who were in service as on 14-12-1988 and who have crossed the age of 48 years as on that date be exempted from passing the said examination. In respect of other employees, a concession has been given to pass the said examination, on their promotion to the next higher category, within five years from the date of introduction of examination, i. e. 14-12-1988. ( 7 ) SOME of the employees who were unable to pass the said examination and acquire the said qualification approached the Andhra Pradesh Administrative Tribunal and questioned the very action of the Government in introducing the scheme of the said examination. ( 7 ) SOME of the employees who were unable to pass the said examination and acquire the said qualification approached the Andhra Pradesh Administrative Tribunal and questioned the very action of the Government in introducing the scheme of the said examination. Some of the employees who have already passed the said examination have also approached the Tribunal for enforcement of G. O. Ms. No. 316, dated 14-12-1988 as modified in G. O. Ms. No. 154, dated 11-4-1991. Their contention was that only such of those employees who have passed the said examination alone should be considered for promotion. The Tribunal by common a Judgment dated 2-12-1991 clarified that the service conditions of the employees of the Treasuries and Accounts Department are regulated by the special rules and unless the said rules themselves are amended incorporating the requirement of passing the said examination, it is not open to the government to effect the changes in the procedure for promotion by way of administrative instructions, as has been done by the government by issuing G. O. Ms. No. 316, dated 14-12-1988. The Tribunal accordingly held that the executive instructions issued by the government contained in G. O. Ms. No. 154, dated 11-4-1991 are of no consequence since the service conditions are regulated by the statutory rules made under the proviso to Article 309 of the Constitution of India. ( 8 ) THEREAFTER, the rule making authority in exercise of the power conferred by proviso to Article 309 of the Constitution of India made the amendments to the said rules by adding proviso to Rule 6 of the rules providing that "all those persons who have crossed the age of 48 years as on the date of issue of these orders shall be exempted from passing the Treasuries and Accounts Service examination, Part I and II, provided that the persons promoted or appointed by transfer to any of the category of posts to which the said test is prescribed shall be reverted back to the lower post in case of their failure to pass the said Test within two years from the date of issue of these orders. " Certain amendments were made to the Annexure to the Rules also, with which we are not concerned for the present. " Certain amendments were made to the Annexure to the Rules also, with which we are not concerned for the present. ( 9 ) SOME of the employees who have already passed the said examination have again approached the Andhra Pradesh Administrative Tribunal seeking appropriate directions that their cases should be considered for promotion to the next higher post and no unqualified person should be promoted in view of the requirement of passing the said examination under the Rules in O. A. No. 6520 of 1994. The Tribunal disposed of the said Original Application to the effect that consequent on amendment to the Special Rules contained and notified in G. O. Ms. No. 328, dated 23-9-1994 only qualified persons should be promoted and if any unqualified persons are promoted in the meanwhile, they should be reverted and replaced by qualified persons in accordance with the Rules. ( 10 ) THE Government of Andhra Pradesh having considered the representation of the Andhra Pradesh Treasuries Subordinate Service Association once again decided in principle to grant exemption to all members of the Treasuries and Accounts Service who were in service as on 14-12-1988 from the purview of requirement of passing the said examination as pre-condition for promotion to the next higher category. The exemption was also made applicable to the employees who were appointed by transfer, provided they were in service as on 14-12-1988. This was by way of executive instructions vide G. O. Ms. No. 260, dated 26-11-1995. The Government accordingly expressed its intention to effect the necessary changes in the statutory rules wherever necessary. ( 11 ) SOME of the members of the service questioned the validity of G. O. Ms. No. 260, dated 26-11-1995 in the Andhra Pradesh Administrative Tribunal in O. A. No. 6456 of 1995 on the ground that the executive order issued by the government has no legal sanctity in the absence of amendment to the special rules and it cannot override the criteria prescribing eligibility conditions for promotion to the next higher post as provided for in the statutory rules. ( 12 ) IN the meanwhile, the rule making authority in exercise of the power conferred by proviso to Article 309 of the Constitution of India made necessary amendments to the rules, which are to the following effect:"in rule 6 of said rules for the two provisos the following shall be substituted, namely:- "provided that all members of the Treasuries and Accounts Services who were in service as on 14-12-1988 including to those who were appointed by transfer shall be exempted from passing the Treasuries and Accounts Service Examinations, Part-I and Part-II for promotion or appointment by transfer to the category of posts to which the said Test is prescribed. " ( 13 ) THE petitioners herein filed O. A. Nos. 5312 of 1996 and 383 of 1996 respectively before the Andhra Pradesh Administrative Tribunal questioning the constitutional validity of the amended rule. The Tribunal by the impugned Judgment, which is a common Judgment in several cases, upheld the said amendment. The amendment is held to be valid. The Tribunal consequently directed the authorities concerned to reinstate such of those employees including the reverted employees into the promoted posts. ( 14 ) THE petitioners herein challenge the correctness of the said judgment of the Tribunal in these writ petitions. It is contended that the proviso added to Rule 6 of the Rules is arbitrary and unconstitutional as it defeats the very purpose of the statutory rule prescribing the examination as a pre-condition for promotion to the next higher post. It is also contended that there is no basis or reason in fixing the cut off date and exempting all the employees of the department from the last grade service onwards from the requirement of passing the said examination, when several employees have already passed the said examination and qualified themselves in the examination held during the period from 1989 to 1994. The impugned proviso amounts to disqualifying the qualified and promoting the unqualified employees. The proviso is irrational and, therefore, is liable to be struck down. The impugned amended rule adversely affects the merit and efficiency of the employees and places the qualified and unqualified employees on the same footing and for the said reason; the Rule is violative of Article 14 of the Constitution of India. The proviso is irrational and, therefore, is liable to be struck down. The impugned amended rule adversely affects the merit and efficiency of the employees and places the qualified and unqualified employees on the same footing and for the said reason; the Rule is violative of Article 14 of the Constitution of India. ( 15 ) SRI M. R. K. Choudary, learned Senior Counsel appearing on behalf of the petitioners in W. P. No. 21753 of 1997 contended that the benefits acquired by the petitioners, who have passed the examination in accordance with the existing rules entitling them for consideration of their cases for promotion to the next higher post, cannot be taken away by the amended rule with retrospective effect. The rule making authority by substituting the impugned proviso totally destroyed the very scheme of conducting the examination and requirement to pass the same for the purposes of consideration of one s case for promotion to the next higher post. The whole object of the main rule is defeated by the impugned proviso. It is contended that the amendment is nothing but a colourable exercise of power by the rule making authority. ( 16 ) SRI Vedula Venkataramana, learned counsel for the petitioner in W. P. No. 26697 of 1997 contended that there is no rational basis or reason in prescribing the cut off date (14-12-1988) and exempting all the employees of the department from the last grade service onwards from the requirement of passing the examination. The amended rule, according to the learned counsel for the petitioner, is irrational and, therefore, liable to be struck down being violative of Article 14 of the Constitution of India. ( 17 ) IT is the case of the State Government that the rules including the impugned proviso were issued by the rule making authority to safeguard the interest of the senior most members of the services who have been serving the department for the last more than 20 years. The rule making authority having adverted to all the relevant facts and in view of the repeated representations received from the various service associations had decided to grant exemption for those employees who were in service as on 14-12-1988. The rule making authority having adverted to all the relevant facts and in view of the repeated representations received from the various service associations had decided to grant exemption for those employees who were in service as on 14-12-1988. It has explained the significance of the date 14-12-1988 being the date of introduction of the new examination required to be passed by the employees for consideration of their cases for promotion to the next higher post. The grant of exemption is based on proper classification and intended mainly in favour of those employees who were in service as on 14-12-1988. It is a valid classification. The intendment of the amendment is to protect the interest of such of those employees who were in service as on 14-12-1988. ( 18 ) IT is further submitted that the requirement of passing the examination for consideration of the cases of the employees for promotion to the next higher post was prescribed on 14-12-1988 by an executive order. Originally there was no rule as such in the statutory rules prescribing the said examination as one of the qualifications for promotion to the next higher post. It is contended that the amended rule has not resulted in causing any prejudice whatsoever in any manner to the case of the petitioners. ( 19 ) IT is further submitted that many posts of Sub-Treasury Officers were vacant and much administrative inconvenience is being caused due to non-filling up of those vacancies. ( 20 ) FURTHER, so far as the case of the petitioners in W. P. No. 21753 of 1997 is concerned, the respondents submit the facts in detail, which are to the following effect:"the petitioners belong to the Zone-III. In respect of Zone-III, a panel of 29 persons has been approved by the appointing authority as per the statutory rules governing the post of Sub Treasury Officer duly considering the persons in the Zone of consideration. The applicants have not come up in the zone of consideration as they were appointed to the category of Senior Accountants (feeder category to the STO) during the year 1986 and 1987 and whereas the persons appointed during the year 1981 and 1982 have only come up for consideration and inclusion in the panel for the year 1996-97. The post of Sub Treasury Officer is governed by the A. P. T and A (Sub) Service Rules. The post of Sub Treasury Officer is governed by the A. P. T and A (Sub) Service Rules. According to Rule 5 of Andhra Pradesh State and Subordinate service Rules, 1996 promotion/appointments to state service shall be made on grounds of merit and ability and the promotions to the post other than in state service shall be made in accordance with seniority-cum-fitness. And accordingly the post of Sub-Treasury Officer is to be filled up basing on the seniority and fitness of the individuals. The Regional Joint Director, Region-II at Cuddapah, has communicated seniority lists of Senior Accountants from time to time in Zone-III vide Memo No. (1) 1995/81/a1 dated 28-12-1981, (2) A1/921/90, dated 2-7-1993 and (3) A2/359/96-1, dated 7-9-1996. He has also issued a combined seniority list of Senior Accountants vide his Memo No. A2/6988/97, dated 17-11-1997. As per this combined seniority list Sri Y. Markandeyulu, stood at Sl. No. 172 and Sri P. Hari Babu stood at Sl. No. 177. Since Sri Y. Markandeyulu, stood at Sl. No. 172 and Sri Hari Babu stood at Sl. No. 177 as per the combined seniority list they are far juniors in the list of S. As in Zone-III of Treasuries and Accounts Sub-Service than the last S. A. promoted as STO in Zone-III from the panel 1996-97. The S. As promoted as STOs from the panel for the year 1996-97 are at Sl. Nos. 36 to 74 of the combined seniority list communicated by the R. J. D. Cuddapah. Even if the promotions were considered without observing the exemption given in G. O. Ms. No. 16 dated 20-1-1996 and if promotions were considered promoting the Senior Accountants who have crossed the age of 48 years as on 1-9-1996 i. e. (panel year for 1996-97) in pursuance of the G. O. Ms. No. 328 dt. 23-9-1994, the applicants names would not have come up for promotion as there were (71) Senior Accountants who have crossed the age of (48) years as on 1-9-1996 (from Sl. No. 36 to 171) above the applicants and eligible for inclusion in the panel for 1996-97 as against the 29 vacancies in the Zone-III. No. 328 dt. 23-9-1994, the applicants names would not have come up for promotion as there were (71) Senior Accountants who have crossed the age of (48) years as on 1-9-1996 (from Sl. No. 36 to 171) above the applicants and eligible for inclusion in the panel for 1996-97 as against the 29 vacancies in the Zone-III. " ( 21 ) IN nutshell, the respondents contend that the exemptions were granted by prescribing the cut off date only to facilitate and to protect the larger segment of the employees of the department who have been serving the department for the last more than twenty years. Further, the examination was introduced for the first time as additional qualification besides Accounts Test for Subordinate Officers, Part I and II for those employees who were already in service and already passed the Accounts Test Part I and II. ( 22 ) SRI D. Prakash Reddy, learned Additional Advocate General appearing on behalf of the State contends that the petitioners miserably failed to establish as to how the impugned amended rule suffers from any arbitrariness adversely effecting their rights. The petitioners are admittedly continue to be in service ever since 14-12-1988 and are entitled for the benefit of the amended rule. Merely because the petitioners have acquired the prescribed additional qualification pursuant to the administrative instructions issued by the government, they have not acquired any vested right for promotion to the next higher post based on acquisition of such additional qualifications. It is contended that if the rule making authority has power to prescribe the qualifications required to be possessed for a post, it has the power to amend the rule even with retrospective effect. The learned Additional Advocate General contends that the courts in exercise of their jurisdiction under Article 226 of the Constitution of India cannot judicially review even the legislative inputs. It is submitted that the government experienced administrative inconvenience in filling up of the vacancies of Superintendents/sub-Treasury Officers since many of the employees failed to acquire the prescribed qualifications. The learned Additional Advocate General contends that the courts in exercise of their jurisdiction under Article 226 of the Constitution of India cannot judicially review even the legislative inputs. It is submitted that the government experienced administrative inconvenience in filling up of the vacancies of Superintendents/sub-Treasury Officers since many of the employees failed to acquire the prescribed qualifications. The interest of the large number of employees of the department has been adversely affected on account of the decision of the government in prescribing a pass in the written test as a qualification for promotion to the next higher post and the government having realised the difficulties of the employees thought it desirable to protect the interest of such of the senior employees and accordingly exempted from the purview of the examination with reference to cut off date. It is contended by the learned Additional Advocate General that the amendment of the rule is by substitution and it shall be deemed to have been incorporated in the rules granting exemption from passing of the examination to such of those employees who were in service as on 14-12-1988. ( 23 ) BEFORE we proceed further to examine the constitutional validity of the impugned proviso, it may be necessary to appreciate the nature of the rule making power, so far as the services under the Union or any State, are concerned under Article 309 of the Constitution of India, which provides as under:"309. ( 23 ) BEFORE we proceed further to examine the constitutional validity of the impugned proviso, it may be necessary to appreciate the nature of the rule making power, so far as the services under the Union or any State, are concerned under Article 309 of the Constitution of India, which provides as under:"309. Recruitment and conditions of service of persons serving the Union or a State.- Subject to the provisions of this Constitution, Acts of the appropriate Legislature may regulate the recruitment, and conditions of service of persons, appointed, to public services and posts in connection with the affairs of the Union or of any State: Provided that it shall be competent for the President or such person as he may direct in the case of services and posts in connection with the affairs of the Union, and for the Governor of a State or such person as he may direct in the case of services and posts in connection with the affairs of the State, to make rules regulating the recruitment, and the conditions of service of persons appointed, to such services and posts until provision in that behalf is made by or under an Act of the appropriate Legislature under this article, and any rules so made shall have effect subject to the provisions of any such Act. " ( 24 ) THE power conferred upon the Governor by proviso to Article 309 of the Constitution of India to make rules regulating the recruitment and conditions of service of persons appointed to public services and posts, in connection with the affairs of the State is essentially legislative in character. It is a legislative function. The power under Article 309 of the Constitution of India cannot be exercised by the Governor, if the legislature has already made a law and the field is occupied. The power conferred upon the Governor by proviso to Article 309 of the Constitution of India is different from the rule making power that may be given under an enactment. The rules made in exercise of the rule making power given under an enactment constitute delegated or subordinate legislation. The rules framed under Article 309 of the Constitution of India cannot be treated to fall in that category. It is true, like an Act made by the Parliament or the State legislature, it may lay down the conditions of service. The rules made in exercise of the rule making power given under an enactment constitute delegated or subordinate legislation. The rules framed under Article 309 of the Constitution of India cannot be treated to fall in that category. It is true, like an Act made by the Parliament or the State legislature, it may lay down the conditions of service. The rules made by the President or the Governor in exercise of the power provided under Article 309 of the Constitution of India are required to be in conformity with the other provisions of the Constitution of India subject to Articles, 14, 16, 311 and 312. The power of the Governor to legislate , in exercise of the power under the proviso to Article 309 of the Constitution of India, is only subject to the other provisions of the Constitution of India, Acts of the appropriate legislature. The test to determine the constitutionality of any provision of the Rules framed under Article 309 of the Constitution of India is, whether the legislature could have enacted such a provision. ( 25 ) THE Supreme Court in R. L. Bansal V. Union of India1 indicated the grounds on which a rule made under proviso to Article 309 of the Constitution of India can be struck down. It is observed that "now it is true that rules made under the proviso to Article 309 of the Constitution being legislative in character cannot be struck down merely because the Court thinks that they are unreasonable, - and that they can be struck down only on the grounds upon which a legislative measure can be struck down. " ( 26 ) THE rules so made by the Governor in exercise of the power under proviso to Article 309 of the Constitution of India cannot be challenged and struck down on the ground of mala fides. ( 27 ) THE rules framed in exercise of the power under proviso to Article 309 of the Constitution of India can be struck down only on the ground of constitutional infirmities. Whereas the validity or otherwise of delegated legislation, i. e. , the rules framed by the rule making authority under the Act can be struck down on the grounds of (a) substantive ultra vires; and (b) procedural ultra vires. Whereas the validity or otherwise of delegated legislation, i. e. , the rules framed by the rule making authority under the Act can be struck down on the grounds of (a) substantive ultra vires; and (b) procedural ultra vires. It is not necessary in the instant case to further dilate as to the grounds of substantive ultra vires on which a subordinate legislation could be struck down and also as to about the procedural ultra vires. ( 28 ) IT is one of the contentions urged by Sri M. R. K. Choudary, learned Senior Counsel appearing on behalf of the petitioners that the action of the authorities in introducing the impugned provision amounts to an action playing fraud on the provision and also leads to colourable exercise of power conferred upon the rule making authority. ( 29 ) IN the affidavit filed in support of the writ petition, it is stated that "the action of the authorities in introducing such impugned provision amounts to an action playing fraud on the provisions and also leads to colourable exercise of power conferred upon the rule making authorities. " ( 30 ) THE question that falls for consideration is as to whether the rules framed in exercise of the power under proviso to Article 309 of the Constitution of India can be struck down on the ground of colourable exercise of power? ( 31 ) BUT what is colourable exercise of power? ( 32 ) WHERE a statutory power is exercised by the authority ostensibly for the purpose for which it was conferred, but in reality for some other purpose, it is called colourable exercise of power. If the statutory power conferred upon an authority is exercised in an improper manner or for collateral purpose, there is colourable exercise of power. The rules made in exercise of the power under proviso to Article 309 of the Constitution of India cannot be struck down on the ground of colourable exercise of power, since the power exercised for making rules under the proviso to Article 309 of the Constitution of India is legislative in character. ( 33 ) THERE is a clear distinction between colourable exercise of power and colourable legislation . It is well settled that the doctrine of colourable legislation does not involve any question of bona fides or mala fides on the part of the legislature. ( 33 ) THERE is a clear distinction between colourable exercise of power and colourable legislation . It is well settled that the doctrine of colourable legislation does not involve any question of bona fides or mala fides on the part of the legislature. "the whole doctrine resolves itself into the question of competency of a particular legislature to enact a particular law. If the legislature is competent to pass a particular law, the motives which impelled it to act are really irrelevant. On the other hand, if the legislature lacks competency, the question of motive does not arise at all. Whether a statute is constitutional or not is thus always a question of power. " ( 34 ) EXPLAINING the import of the doctrine of colourable legislation , Krishna Iyer, J in R. S. Joshi V. Ajit Mills observed:"in this branch of law, colourable is not tainted with bad faith or evil motive ; it is not pejorative or crooked. Conceptually, colourability is bound up with incompetency. . . . . . . . . . . In Indian terms, it is maya. In the jurisprudence of power, colourable exercise of or fraud on legislative power or more frightfully, fraud on the Constitution, are expressions which merely mean that the legislature is incompetent to enact a particular law although the label of competency is struck on it, and then it is colourable legislation. It is very important to notice that if the legislature is competent to pass the particular law, the motives which impel it to pass the law are really irrelevant. To put it more relevantly to the case on hand, if a legislation, apparently enacted under one Entry in the List, falls in plain truth and fact, within the content, not of that Entry but of one assigned to another legislature, it can be struck down as colourable even if the motive were most commendable. In other words, the letter of the law notwithstanding, what is the pith and substance of the Act? Does it fall within any entry assigned to that legislature in pith and substance, or as covered by the ancillary power implied in that Entry?. . . . . . . . . . . Malice or motive is beside the point, and it is not permissible to suggest Parliamentary incompetence on the source of mala fides. " (Emphasis is of mine ). . . . . . . . . . . Malice or motive is beside the point, and it is not permissible to suggest Parliamentary incompetence on the source of mala fides. " (Emphasis is of mine ). ( 35 ) NOTHING is suggested as to how the impugned proviso, which is legislative in character is a colourable legislation. It is nobody s case that the rule suffers from lack of legislative competence. Therefore, the rule cannot be struck down on the ground of colourable exercise of power. The submission, in our considered opinion, is misconceived. ( 36 ) IT is further contended that the rights or benefits which have already been acquired by the petitioners under the existing rules cannot be taken away by introducing a proviso by way of an amendment with retrospective effect. We have already noticed that the proviso is introduced by way of substitution for the two provisos in Rule 6 of the said Rules. ( 37 ) IT is very well settled that the substitution of a provision results in repeal of the old provision and its replacement by the new provision. Substitution thus combines the repeal and fresh enactment. ( 38 ) THE learned counsel for the petitioners, however, relied upon the judgments of the Supreme Court in S. B. Patwardhan V. State of Maharashtra; T. R. Kapur V. State of Haryana; and P. D. Aggarwal V. State of U. P. in support of their submission that the accrued rights cannot be taken away by amending the rules with retrospective effect and such taking away of the rights amounts to alteration of conditions of service. We are unable to persuade ourselves to accept the submissions made by the learned counsel. In P. D. Aggarwal (11 supra) the Supreme Court in categorical terms observed that "the government has got the power under Proviso to Article 309 of Constitution to make rules and amend the rules giving retrospective effect. Nevertheless, such retrospective amendments cannot take away the vested rights and the amendments must be reasonable, not arbitrary or discriminatory violating Articles 14 and 16 of the Constitution. "in the very same judgment, it is observed that "the authority competent to lay down qualifications for promotion is also competent to change the qualifications. The rules defining qualifications and suitability for promotion are conditions of service and they can be changed retrospectively. "in the very same judgment, it is observed that "the authority competent to lay down qualifications for promotion is also competent to change the qualifications. The rules defining qualifications and suitability for promotion are conditions of service and they can be changed retrospectively. The said rule is however subject to a well-recognised principle that the benefits acquired under the existing rules cannot be taken away by an amendment with retrospective effect. Such rules laying down qualifications for promotion made with retrospective effect must necessarily satisfy the tests of Articles 14 and 16 (1) of the Constitution. " ( 39 ) IT may have to be borne in mind that whenever any Act or amendment is brought in force retrospectively or any provision of the Act is deleted retrospectively, in this process rights of some are bound to be affected one way or the other. In every case, it cannot be urged that the exercise by the legislature while introducing a new provision or deleting an existing provision with retrospective effect per se shall be violative of Article 14. If that stand is accepted, then the necessary corollary shall be that legislature has no power to legislate retrospectively, because in that event a vested right is effected. ( 40 ) IT is required to notice that in the instant case the Government of Andhra Pradesh for the first time has issued G. O. Ms. No. 316, dated 14-12-1988 prescribing the eligibility of a pass in the said examination for promotion of Senior Accountants to the next higher post. It is for the first time, an examination named as "treasuries and Accounts Service Examination" consisting of Part I and II has been introduced by way of executive instructions. Ever since, the issue as to the requirement and competence of the government to prescribe such qualification and making it eligibility criteria for the purpose of consideration of the cases of the employees for future promotions became the subject matter of litigation in the Andhra Pradesh Administrative Tribunal. ( 41 ) WE have already noticed that the very introduction of the examination was challenged. For the first time special rules were amended by making amendment to Rule 6 of the Rules and notified in G. O. Ms. No. 328, dated 23-9-1994. The said special rules were again sought to be amended by way of executive instructions. ( 41 ) WE have already noticed that the very introduction of the examination was challenged. For the first time special rules were amended by making amendment to Rule 6 of the Rules and notified in G. O. Ms. No. 328, dated 23-9-1994. The said special rules were again sought to be amended by way of executive instructions. The said action was challenged and the same has resulted in further amendment of the special rules. It is thus clear that neither the petitioners nor any of the employees working in the department have ever acquired any statutory or vested rights. The rights were never settled and vested. The very decision to hold the examination has been the bone of contention and subject matter of litigation. We are of the considered opinion that by the impugned amendment no vested or settled rights as such are sought to be taken away by the impugned amendment. ( 42 ) THE decision of the Supreme Court in Chairman, Railway Board V. C. R. Rangadhamaiah13 upon which reliance is placed by the learned counsel for the petitioners would in no manner support the case of the petitioners. The Supreme Court, in the said decision, while explaining the scope of retrospective operation of the rules made under Article 309 of the Constitution of India observed:". . . . . . A rule which operates in future so as to govern future rights of those already in service cannot be assailed on the ground of retroactivity as being violative of Articles 14 and 16 of the Constitution, but a rule which seeks to reverse from an anterior date a benefit which has been granted or availed of, e. g. , promotion or pay scale, can be assailed as being violative of Articles 14 and 16 of the Constitution to the extent it is operates retrospectively. " ( 43 ) IN the same decision, the Supreme Court while explaining as to the meaning of expressions vested rights or accrued rights observed:"in many of these decisions the expressions "vested rights" or "accrued rights" have been used while striking down the impugned provisions which had been given retrospective operation so as to have an adverse effect in the matter of promotion, seniority, substantive appointment, etc. , of the employees. , of the employees. The said expressions have been used in the context of a right flowing under the relevant rule which was sought to be altered with effect from an anterior date and thereby taking away the benefits available under the rule in force at that time. It has been held that such an amendment having retrospective operation which has the effect of taking away a benefit already available to the employee under the existing rule is arbitrary, discriminatory and violative of the rights guaranteed under Articles 14 and 16 of the Constitution. " ( 44 ) WE fail to appreciate as to how the said Judgment would support the case of the petitioners. No additional rights as such are conferred upon any of the petitioners either in the matter of granting promotion or pay scales. On the other hand, certain additional qualifications were prescribed making the Treasuries and Accounts Service Examination as one of the conditions for consideration of cases for promotion to the next higher post. It is not a benefit conferred upon any employee. None of the petitioners have acquired any right under the said prescription of a pass in the said examination as a pre-condition for promotion to the next higher post. The rights of the petitioners cannot be said to have become crystallised. The said requirement was not a part of the special rules when the petitioners and other employees were recruited into the service. The amendment to the rule exempting from the requirement has not taken away any vested or accrued rights of the petitioners. It is a case of granting exemption in favour of a definite class of employees who were in service as on 14-12-1988, i. e. , the date on which the said requirement of passing the examination was introduced for the first time by way of executive instructions. ( 45 ) IN our considered opinion, the impugned proviso incorporated into the rules by way of substitution in no manner takes away any of the rights of the petitioners or any of the employees as such. ( 46 ) SRI Vedula Venkataramana, learned counsel for the petitioner in W. P. No. 26697 of 1997, however, relied upon the decisions of the Supreme Court Kedarnath Jute Manufacturing Co. ( 46 ) SRI Vedula Venkataramana, learned counsel for the petitioner in W. P. No. 26697 of 1997, however, relied upon the decisions of the Supreme Court Kedarnath Jute Manufacturing Co. Ltd. V. The Commercial Tax Officer; Ishverlal V. Motibhaiand S. B. K. Oil Mills V. Subhash Chandra in support of his submission that the effect of an excepting or qualifying proviso, according to the ordinary rules of construction, is to except out of the preceding portion of the enactment, or to qualify something enacted therein, which but for the proviso would be within it. The Supreme Court in the said decisions explained that the courts in the process of interpretation cannot rewrite the clause and omit the proviso altogether. Such an interpretation will defeat the express intention of the legislature. The principle laid down in the said judgments in no manner would support or advance the case of the petitioners. ( 47 ) WHETHER the impugned proviso is violative of Article 14 of the Constitution of India. Whether there is no reasonable classification? ( 48 ) THE impugned amendment to Rule 6 of the Rules exempts all the employees who were in service as on 14-12-1988 from the requirement of passing of Treasures and Accounts Service Examination. It is not a case of any hostile discrimination. The petitioners were also in service as on 14-12-1988. They are also entitled for the same benefit of relaxation. The petitioners do not want any such benefit for the reason that they have appeared for the examination and passed the same. By granting relaxation, the rule making authority did not take away any vested or accrued right of the petitioners. The rule making authority, having considered that the additional qualification was prescribed for the fist time on 14-12-1988 in respect of those employees who are already in service, for good and valid reasons, relaxed the qualification of passing of the said examination. It is not a case of class legislation, but a case of reasonable classification and the same satisfies twin tests of classification being founded on an intelligible differentia which distinguishes persons or things that are grouped together from those that are left out of the group and there is a definite rational nexus to the object sought to be achieved by the impugned proviso. ( 49 ) THE decision in D. S. Nakara V. Union of India upon which reliance is placed by the learned counsel for the petitioners would not be of any help to the case of the petitioners. ( 50 ) IT is also contended that the impugned proviso is arbitrary and liable to be struck down as being violative of Article 14 of the Constitution of India. It is well settled that no enactment can be struck down by just saying that it is arbitrary or unreasonable. The enactment cannot be struck down on the ground that the court thinks it unjustified. "some or other constitutional infirmity has to be found before invalidating an Act. " ( 51 ) FOR the aforesaid reasons, we are of the considered opinion that the impugned proviso does not suffer from any legal or constitutional infirmity. The impugned proviso is neither arbitrary nor discriminatory in its nature. The rights of the petitioners in no manner whatsoever are affected by the impugned proviso granting exemption from passing the Treasuries and Accounts Service Examination, Part I and II for promotion and appointment by transfer to the category of post to which the said examination is prescribed in favour of members of the Treasures and Accounts Service who were in service as on 14-12-1988. The impugned proviso does not suffer from any constitutional infirmities. It uniformly applies to such of those employees who were in service as on 14-12-1988. The petitioners are also entitled for the benefit of the amended rule. Mere fact that they have passed the examination conducted by the Andhra Pradesh Public Service Commission is of no consequence and they cannot be characterised as a separate class and subjected to any hostile discrimination as such. ( 52 ) IT is a clear case of granting exemption by the State in favour of a class of employees by incorporating an appropriate proviso in the special rules. The power to relax the conditions and rules to avoid hardship in any class of cases is well recognised in service jurisprudence. Of course, such power of relaxation is generally contained in the rules with a view to mitigate undue hardship or to meet a particular situation. The exercise of that power may depend upon variety of circumstances. The power to relax the conditions and rules to avoid hardship in any class of cases is well recognised in service jurisprudence. Of course, such power of relaxation is generally contained in the rules with a view to mitigate undue hardship or to meet a particular situation. The exercise of that power may depend upon variety of circumstances. Strict application of rules may create a situation where a particular individual or a set of individuals may suffer undue hardship and further there may be a situation where requisite qualified persons may not be available for appointment to the service. In the absence of a provision in the special rules enabling the authority to grant such relaxation, the Governor made the impugned proviso granting exemption in favour of class of employees in the manner referred to hereinabove. ( 53 ) FOR the aforesaid reasons, we agree with the conclusions of the Tribunal in upholding the constitutional validity of the impugned proviso. ( 54 ) WE do not find any merit in these writ petitions. The same shall accordingly stand dismissed. There shall be no order as to costs.