Judgment :- 1. These Writ Appeals are preferred against the order of learned single Judge in W.P. 11053 of 1996 dated 4.1.1999. 2. Parties herein will be referred according to their ranks in the writ petition. 3. The material facts which are necessary for proper disposal of these appeals could be summarised thus: First respondent is Madras Metropolitan Water Supply and Sewerage Board, a Board created under Madras Metropolitan Water Supply and Sewerage Act, 1878. Under Section 81 of the Act, the Board has been given the right to make Regulations to carry out the purpose of the Act and invoking that power, first respondent has made Madras Metropolitan Water Supply and Sewerage Board Employees Service Regulations, 1978 (hereinafter referred to as ‘Service regulations’). 4. On 29.4.1993, the Board issued proceedings in EP No. 15 of 1993, Personnel and Administration Department, which dealt with study leave and incentives for higher education related to the Board. he Board has also formulated Regulations by name Madras Metropolitan Water Supply and Sewerage Board Employees Leave Regulations (hereinafter referred to as ‘Leave regulations’)-Regulation 9 of the Leave Regulations as it stood before 29.04.1993 reads thus, “Study Leave:— Study leave, on half pay may be granted, at the discretion of the Board, to staff in pay scales the minimum of which is Rs. 600 or more who desired to undergo a special course of higher studies or specialised training in a professional and technical subject having a direct and close connection with their share of duty. Study leave is not admissible for pursuit of academic courses unrelated to the employees work. The maximum study leave admissible will be 24 months during the entire service of an employee and it may be granted upto 12 months at any one time. Before proceeding on study leave, an employee must furnish an undertaking to the Board agreeing to serve the Board for not less than five years after his return from leave. If the Board considers that the course of study or training for attending, which study leave is granted, is of particular relevance to an employee for his efficient functioning, it may permit such employee to draw full pay for the entire period of his leave.” On 29.4.1993, the Board passed a resolution amending Regulation 9. If the Board considers that the course of study or training for attending, which study leave is granted, is of particular relevance to an employee for his efficient functioning, it may permit such employee to draw full pay for the entire period of his leave.” On 29.4.1993, the Board passed a resolution amending Regulation 9. The amended Regulation 9 reads thus, “Study Leave:— Study leave, on half pay may be granted, at the discretion of the Board, to staff in pay scales the minimum of which is Rs. 2,000/- or more who desire to undergo a special course of higher studies or specialised training in a professional and technical subject having a direct and close connection with their duty. Study leave is not admissible for pursuit of academic courses unrelated to the employees work. The maximum study leave admissible will be 24 months during the entire service of an employee and it may be granted upto 12 months at any one time. Before proceeding on study leave, an employee must furnish an undertaking to the Board agreeing to serve the Board for not less than five years after this return from leave. The above guidelines is only made applicable to persons proceeding on study leave on their own.” c) Recognition of Post Graduate qualification acquired while in service :— Once a candidate acquires a First Class Post graduate Engineering qualification, he will get two years extra weightage in terms of seniority which will be counted for elevation. If he acquires a second class post graduate Engineering qualification, he will get one years extra weightage for this purpose. If he does not qualify (after availing study leave), the entire salary drawn during the study leave period will be recovered. d) Miscellaneous: An eligible candidate whose application has been sent with prior permission of the Board and has been accepted by the University should execute a Bond, before he joins the University to serve the Board for a minimum period of five years on his rejoining service after study leave. If he wants to quit within this period, he should refund the expenses incurred by the Board on him during his study period. The candidates will be permitted to draw stipend or allowances granted by the institution in addition to the leave salary. The amendments will be effective from 1.4.1993 and will not be made applicable to the past cases.” 5. The candidates will be permitted to draw stipend or allowances granted by the institution in addition to the leave salary. The amendments will be effective from 1.4.1993 and will not be made applicable to the past cases.” 5. It is the case of writ petitioners that on the basis of this amended Regulations, petitioners applied for leave and got admission in the various colleges to get Post-Graduate Engineering qualifications. It is their case that the amended leave Regulation 9 was in the nature of incentive offered to them and basing on the said Regulation when they sought for study leave, the same was also granted by first respondent as per proceedings dated 3.8.1994 and they were relieved from services of Board and permitted to join various Universities for the purpose of completing their Post Graduate Engineering. At the time of issuing proceedings dated 3.8.1994, it was stated that if they acquire First Class Post Graduate Engineering qualification, they will get two years weightage in terms of seniority which will be counted for elevation and if they acquired Second Class Post Graduate Engineering qualification, they will get one year extra weightage in seniority and if they do not qualify after availing study leave, the entire salary drawn during the study leave period will be recovered. It also provides that they should execute a bond to serve the Board for a period of five years and if they quit the services of the Board within that period, they should refund the expenses incurred by the Board on them during their study period. It is their case that all these petitioners commenced the course and completed the course in 1996 and all the petitioners obtained first class. 6. Reason for filing the writ petition is that the proceeding dated 29.4.1993 was rescinded by the Board as per proceedings in BP 8/95, dated 10.3.1995. By virtue of proceedings dated 10.3.1995, original leave Regulation No. 9 was restored. According to petitioners, the restoration of original Regulation No. 9 has affected their chance of promotion and also seniority. It is their case that all assurances granted to petitioners were wiped away. Petitioners have acted to their detriment by joining course of study in the hope that they will be given the benefit of seniority and in view of subsequent proceedings, their hopes have been nullified. It is their case that all assurances granted to petitioners were wiped away. Petitioners have acted to their detriment by joining course of study in the hope that they will be given the benefit of seniority and in view of subsequent proceedings, their hopes have been nullified. Petitioners, therefore, moved representations to first respondent for which there was no reply. 7. In the various grounds taken in the writ petition, it is said that the principles of promissory estoppel and equitable estoppel will apply to the facts and circumstances of the case. First respondent has held out a categorical assurance and promise that if a person qualifies himself in Post Graduate degree course, he will be given the benefit of weightage in seniority and this benefit had a number of conditions attached to it, such as half pay, execution of bond for five years, etc. Since petitioners have acted on the basis of promise made by first respondent and at all stages, they were under the impression and were made to understand that on passing the course, they would get weightage of seniority and having undergone the course and having acted on the basis of the promise held out by respondent, the Board cannot go back on those promises and withdraw the benefits already granted. It is further said that though the amendment is not retrospective, it has been made retro-active by stating that the revised rule will apply even to those who are already undergoing the course of study. It is their case that the Act prohibits the Board to make Regulations with retrospective effect. These Regulations have been made in exercise of powers conferred under Section 81 of the Act and it gives powers to the Board to specify the conditions of service of Officers and employees. The said Regulations can come into force on the date when the Regulations have been made by the Board and, therefore, it can only have prospective effect. It is their case that the amendment to the Regulations cannot be made applicable to the persons who have already acted on the earlier Regulations. It is their further case that the retrospectivity of the Regulations should not affect the vested rights of persons. On the basis of Regulation dated 29.4.1993, petitioners have obtained or acquired vested right to have the service conditions regulated in accordance with rules. It is their further case that the retrospectivity of the Regulations should not affect the vested rights of persons. On the basis of Regulation dated 29.4.1993, petitioners have obtained or acquired vested right to have the service conditions regulated in accordance with rules. It is their case that they have also suffered tremendous detriment by acting on the promise and assurance held out by first respondent. Detriments they have suffered are, (1) Bond to be executed by writ petitioners; (2) Half Pay which petitioners received during the course of study; (3) The family suffered on account of half-pay; (4) In the course of failure to pass the course, refund of the entire half pay paid during the course of study; and (5) consequent tension due to the absence of failure in the course. On the basis of these detriments which petitioners suffered, first respondent is not entitled to rescind from the same. The impugned proceeding is also challenged as violative of principles of natural justice, 8. For the above reasons, petitioners seek issuance of writ of certiorarified mandamus or any other appropriate writ, order or direction calling for the records of the respondent in proceedings No. BP/8/95 Personnel and Administration Department, dated 10.3.1995, quash the same and further direct respondent to act in accordance with proceedings No. BP/15/93, Personnel and Administration Department, dated 29.4.1993, by giving the benefit of seniority and other benefits and pass such further or other orders as may be deemed fit and proper. 9. Counter affidavit was filed by first respondent wherein they have narrated the circumstances under which they had to rescind the earlier Leave Regulation, No. 9. In the counter affidavit, it is said that there are many Post Graduate Engineers working in the Board and if the amended Regulation dated 29.4.1993 is implemented, it will adversely affect the Senior Engineers who are already having Post Graduate Engineering qualifications, and mey will become juniors to the persons who have completed post graduation on being sponsored by the Board. Taking into consideration the above circumstances, it became necessary to reconsider the proceedings in BP 15/93 in order to avoid any complication in fixing seniority. It is further said that proceeding BP 15/93 is only amendment to Leave Regulation and not to Service Regulations. Board also justified in passing proceedings in BP 8/95 taking into consideration the interest of administration of Board. It is further said that proceeding BP 15/93 is only amendment to Leave Regulation and not to Service Regulations. Board also justified in passing proceedings in BP 8/95 taking into consideration the interest of administration of Board. It is also said that due to the liberalised Leave Regulations, certain practical difficulties arose in implementing the amended leave regulation. There are persons in service with Post Graduate qualification in Engineering and the amended Regulation could not be made applicable to them and this amounts to inequality among the Engineers of Senior Cadre. It was also brought to the notice of the Board that there are more applications to join M.E./M/Tech. courses and study leave in en masse will dislocate the normal functioning of Engineering wing of the Board. It is also said that to ensure fairness in fixation of seniority and to avoid disputes in fixing seniority and to avoid dislocation in normal functioning of the Board, it was decided to rescind the proceedings already issued. 10. It is also said that the Graduate Engineers who have been deputed for higher education on the basis of amended Regulation No. 9 as per proceedings BP 15/93, had adversely affected the senior Engineers who are also Post Graduates. Proceedings in BP 15/93 also should not affect the existing employees and taking into consideration the over all benefit, the Board decided to rescind proceedings in BP 15/93. The principle of promissory estoppel also cannot be invoked since it is against law. It is also said that the principle of natural justice also may not have any application since the Board is given the power to change the regulation without notice and no notice is also required to be given to the employees. It prayed for dismissal of the writ petition. 11. Along with the writ petition, WMP 14780 of 1996 was filed for interim direction to Board to give effect to proceedings BP 15/93 dated 29.4.1993 and consequently grant benefit of seniority in accordance with the said order. The said WMP was dismissed by learned Judge of this Court and learned Judge held that unless and until the writ petition is decided in favour of petitioners, petitioners will not be entitled to interim relief which they have sought for in WMP. It is further held that main relief in writ petition and WMP are same and the same cannot be granted in interlocutory stage. It is further held that main relief in writ petition and WMP are same and the same cannot be granted in interlocutory stage. 12. While so. Association of Assistant Engineers, represented by its General Secretary and one Assistant Engineer took out a petition in WMP 19485 of 1996 to implead themselves in writ petition as well as in the Miscellaneous Petition. They have subsequently been impleaded. 13. After respondents 2 and 3 were impleaded, writ petitioners filed WMP 20114 of 1998 for grant of injunction restraining first respondent from making any promotions to the post of Executive Engineer, pending disposal of writ petition. Learned Judge of this Court, as per order dated 13.11.1998 dismissed the said application holding that no interim order could be granted. Learned Judge held that any appointment made by first respondent during pendency of writ petition will always be subject to the result of writ petition. Learned Judge also directed to post the main writ petition for disposal. 14. Additional respondents who were impleaded also supported the case of the Board and contended that the amended Regulation No. 9 passed by the Board as per proceedings No. 15/93 is really discriminatory and the same is not valid. A Regulation cannot be passed affecting the vested right of those Engineers who are equally placed with that of writ petitioners. Merely because petitioners got qualified after 1.10.1993 by acquiring Post Graduate Engineering qualification, their seniority should not be affected when the rule of seniority is provided under the General Rules as provided under the Service Regulations. 15. Learned single Judge as per order dated 4.1.1999 allowed the writ petition on the ground of promissory estoppel. Learned Judge held that the Board has held out to petitioners that they will be given service weightage if they obtain Post Graduate Engineering qualification either First Class or Second Class and that right which they had obtained cannot be taken away by subsequent amendment to the Leave Regulations nor earlier resolution could be rescinded to their detriment. Learned Judge further held that petitioners have acted on the assurance given by the Board and the vested right cannot be taken away by amending the Regulations with retrospective effect. Learned Judge further held that petitioners have acted on the assurance given by the Board and the vested right cannot be taken away by amending the Regulations with retrospective effect. Proceedings of the Board in BP 8/95 dated 10.3.1995 was, therefore, quashed, and first respondent was directed to act in accordance with proceedings in BP 15/93 dated 29.4.1993 by giving benefit of seniority and other benefits. Two months time was granted to first respondent to comply with the directions. 16. It is against the said order of learned single Judge, these Writ Appeals are preferred. 17 . W.A. 104 of 1999 is filed by additional respondents 2 and 3 and W.A. 204 of 1999 is filed by a Post Graduate Engineer who is affected by the decision of the learned single Judge. 18. In W.A. 104 of 1999, appellants filed C.M.P. 841 of 1999 to grant interim stay of operation of order oflearned single Judge. As per order dated 22.1.1999, interim stay was granted until further orders. 19. Petitioners in writ petition filed counter to CMP 841 of 1999 and moved an application to vacate the stay. Since the argument on interim application as well as main Writ Appeal being the same, with consent of parties, both Writ Appeals were heard. 20. Learned counsel for appellants in W.A. 104 of 1999 submitted that there is no scope for applicability of principle of promissory estoppel in this case. It is argued that there are many senior Post Graduate Engineers working in the Board and the seniority list has also been published, which has become final. That seniority cannot be taken away merely because petitioners have been sent for higher studies on the basis of amended Leave Regulation No. 9 as per proceedings in BP 15/93. It is submitted that service Regulations provide for how to reckon seniority and so long as that is not amended, Leave Regulations cannot affect their seniority. It is further submitted that main purpose of issuing proceedings BP 15/93 was to recognise the higher qualification by enhancing the quality of output and to help the employees. It is further said that when an Engineer acquires higher qualification; it enriches the operational capabilities and ability to handle diversity of a predominantly technical organization like the Board. It is further submitted that main purpose of issuing proceedings BP 15/93 was to recognise the higher qualification by enhancing the quality of output and to help the employees. It is further said that when an Engineer acquires higher qualification; it enriches the operational capabilities and ability to handle diversity of a predominantly technical organization like the Board. It is argued that if this is the aim on the basis of which the proceeding dated 29.4.1993 was issued, naturally appellants and other persons similarly situated are also entitled to be considered and the benefit given to petitioners alone will be discriminatory. The amendment which has come into effect from 1.4.1993 has affected their vested rights and that right cannot be taken away. It is further submitted that petitioners also cannot have any vested right since even before they got qualified for higher qualification and before they were given the weightage, the order was rescinded. Petitioners got themselves qualified only in the year 1996 whereas amended regulation was rescinded on 10.3.1995. As per original Regulation No. 9 also, an Engineer who wants to pursue his higher studies will be entitled to half pay and also to execute bond for serving the Board for a period of five years. The only change that is made is regarding service weightage which should not have been provided in the Leave Regulation. How far other Engineers similarly situated were not considered by the Board and when the Board itself found that the special benefit given to petitioners will be inequitable, it thought of rescinding it. 21. Learned senior counsel for appellants in W.A. 204 of 1999 submitted that final seniority list has been published, on 2.9.1987 of Assistant Executive Engineers and the same has become final. It is further argued that the amended Regulation No. 9 as per proceedings BP 15/93 is arbitrary and the same has affected other employees who are far seniors to petitioners. It is also submitted that it is violative of Article 14 of the Constitution of India since it has no nexus to the object which is sought to be achieved. 22. Learned Standing Counsel for the Madras Metropolitan Water Supply and Sewerage Board also supported the arguments of learned counsel for appellants. 23. Learned counsel for writ petitioners fully supported the findings of learned single Judge and prayed for dismissal of Writ Appeals. 22. Learned Standing Counsel for the Madras Metropolitan Water Supply and Sewerage Board also supported the arguments of learned counsel for appellants. 23. Learned counsel for writ petitioners fully supported the findings of learned single Judge and prayed for dismissal of Writ Appeals. It is also argued that when learned Judge has exercised his powers under Article 226 of the Constitution of India, the same is not liable to be disturbed or interfered with lightly. 24. First question that is to be considered is whether the principle of promissory estoppel could be applied in this case and how far the amended Regulation No. 9 as per proceedings in BP 8/95 dated 10.3.1995 is valid? 25. As per the Madras Metropolitan Water Supply and Sewerage Act, 1978, the Board has been constituted for attending to the growing needs and for planned development and appropriate Regulation of water supply and sewerage services in the Madras Metropolitan Area with particular reference to the protection of Public health and for all matters connected therewith or incidental thereto. Under Section 80 of the Act, Government may make Rules to carry out the purposes of the Act. Under Section 81 of the Act, the Board is empowered to make Regulations not inconsistent with the Act for carrying out the purposes of the Act. Under Section 81(2)(c) of the Act, the Board is empowered to make Regulations regarding the method of recruitment, qualifications, the pay, the duties and other terms and conditions of service of officers and employees and the constitution and management of provident fund and other superannuation funds. 26. On the basis of the said provisions, the Board has already framed Regulations for Employees (Discipline and Appeal) Regulations; Pay Regulations; Leave Regulations; Service (Conduct) Regulations; Pension Regulations and also Employees Service Regulations. 26. On the basis of the said provisions, the Board has already framed Regulations for Employees (Discipline and Appeal) Regulations; Pay Regulations; Leave Regulations; Service (Conduct) Regulations; Pension Regulations and also Employees Service Regulations. Regulation No. 3 of Madras Metropolitan Water Supply and Sewerage Board reads thus, “The Madras Metropolitan Water Supply and Sewerage Board Employees (Discipline and Appeal) Regulations, 1978, the Madras Metropolitan Water Supply and Sewerage Board Pay Regulations, 1978, the Madras Metropolitan Water Supply and Sewerage Board Leave Regulations, 1978, the-Madras Metropolitan Water Supply and Sewerage Board Services (Conduct) Regulations, 1978, and the Madras Metropolitan Water Supply and Sewerage Board Pension Regulations 1978 shall, in so far as be applicable and except to the extent specifically provided in these Regulations govern all the staff employees in the Boards services in the matter of pay, leave pension, and other conditions of service.” Regulations Nos. 21 and 22 of the Service Regulations are also relevant for our purpose, which reads thus, “21. Seniority :— a) The seniority of a person in the Boards service with respect to a category or grade shall be determined by the rank obtained by him in the list of approved candidates drawn up by the Board subject to the rule of reservation where it appeals; the date of commencement of his probation shall be the date on which he joins the Boards service irrespective of his seniority. b) The seniority of a person transferred from one class or category to another carrying the same pay or scale of pay shall be reckoned with reference to rank in the class or category from which he is transferred. c) It shall be open to the Managing Director or the authority empowered in this behalf by the Managing Director to fix the seniority of any person in a class, category or grade after giving such persons or any other person likely to be affected an opportunity to make a representation in this regard. An aggrieved employee may prefer an appeal to the Board against the decision of the Managing Director. An aggrieved employee may prefer an appeal to the Board against the decision of the Managing Director. d) Whenever the need arises for the Board to take over the services of officers and staff working in other institutions like the Madras Municipal Corporation, Local Bodies or the State Government, the inter-se-seniority of such officers and staff in any category or grade on the Board” service shall be determined on the basis of the length of service rendered by them in that category or grade in the previous institution. 22. Promotion To Supervisory Or Managerial Grades: — 10% of the promotions subject to a minimum of at least one to Board Services in Managerial grades shall be made on grounds of merit and the balance 90% promotions to these grades and all promotions to the lower grades on the basis of only seniority. Promotions to fill up the vacancies not set apart for merit promotion in the supervisory and managerial categories will also be decided on the basis of seniority. Even for merit promotions, seniority will be the deciding factor as between the candidates eligible for being considered for such promotion. The Board shall be the deciding authority for making merit promotions.” 27. Regulation 21 provides how to reckon seniority and under Regulation No. 22, 10% of the promotions subject to a minimum of at least one to Board Services in managerial grades shall be made on grounds of merit and the balance 90% promotions to these grades and all promotions to the lower grades on the basis of only seniority. Even in respect of 10% merit promotions, seniority will be the deciding factor as between candidates eligible for being considered for such promotions. 28. It is clear from reading of Regulations 3, 21 and 22 of Service Regulations that seniority and promotions are to be governed only by Service Regulations and the same alone shall govern the employees in the Board Services. It is the admitted fact that no amendment has been made to Service Regulations. As per Regulation 21, seniority of a person has to be determined by the rank obtained by him in the list of candidates drawn up by the Board. It is further clear that the length of service in the Board Service shall be the only criteria for considering seniority. That seniority cannot be taken away by any Regulation made in the Leave Regulations. 29. It is further clear that the length of service in the Board Service shall be the only criteria for considering seniority. That seniority cannot be taken away by any Regulation made in the Leave Regulations. 29. The purpose of Regulation No. 9 in Leave Regulation is only to enable the candidate to get higher qualifications. Original Leave Regulation also provides for availing study leave. We have already extracted Regulation No. 9 as it originally stood and which has now been restored by proceedings in BP 8/95. As per the said Rule, during study leave, the candidate will be entitled to only half pay unless the Board for special reasons to be recorded allows the employees to draw full pay for the entire period of study leave. It is also clear from the said Rule that the study leave cannot be granted to employees unless he intends to pursue his higher studies in a professional technical subject having direct and close connection with the share of duties. From the said provision, it is clear that higher qualification could be more useful to the Board and should enrich the operational capability and ability. If that was the position even under original Regulation, what was the necessity for amending Regulation as per proceedings in BP 15/93. It could further be seen that amended Regulation as per proceedings in BP 15/93 was made effective from 1.4.1993 and the same is not made applicable to past cases. The consequence of amendment was drastic. It is not disputed that employees having Post Graduate qualification in environmental engineering are there, long before 1.10.1993. Learned counsel for appellants brought to our notice that out of 39 Post Graduate holders, 18 are already having same specialisation in Post Graduate degree i.e., environmental engineering and the names of 18 employees who are already in service long before petitioners came, are also brought to our notice. Even though they are Post Graduates, in Environmental Engineering, they are not given the benefit of amended Regulation as per proceedings BP 15/93. If the purpose is to grant incentive to higher qualified employees, which enriches the operational capability and ability, the same cannot be denied to employees who are seniors to petitioners merely because they have acquired qualification before petitioners. What is the nexus that is to be achieved by amending Regulation as per proceeding No. 15/93 and to make effective from 1.4.1993? What is the nexus that is to be achieved by amending Regulation as per proceeding No. 15/93 and to make effective from 1.4.1993? It is made clear that it will not be applicable to past cases; why seniors, who possess the same qualifications are to be left out are not explained by writ petitioners. Appellants have also brought to our notice the seniority list of Assistant Engineers as on 2.9.1987 published by first respondent, which has now become final. These writ petitioners are juniors to most of the appellants and they are now claiming seniority only by virtue of proceedings in BP 15/93 on the ground that they became Post Graduates after 1993. 30. Board has also stated that before passing proceedings BP. 15/93, it has not considered the seniority and other relevant facts so far as other senior post graduates are concerned and they came to know about this anamoly only when various representations were received from seniors. It is also argued by learned counsel that seniority has to be fixed only on the basis of Service Regulations and any provision in the Leave Regulation should not be inconsistent with Service Regulations. Apart from the same. Service Regulations got overriding effect in regard to matters provided therein. We find force in the said submission. It is not disputed that first respondent has passed Madras Metropolitan Water Supply and Sewerage Board Employees Service Regulations which deal with Engineering and technical services which provide for qualification for promotion to various posts. These Special Regulations also provide for qualification and other requirements for further promotions. Taking into consideration above fact, what was the necessity for giving service weightage for employees getting higher qualification after 1993 is also a matter which ought to have been explained by petitioners. 31. Employees who are similarly situated and who had acquired same qualification earlier and who are seniors to writ petitioners are losing seniority only because of writ petitioners who have obtained post-graduate qualification after 1993. We do not think that the Board is justified in passing such regulations which is purely arbitrary. When the anamoly has been found out, Board thought of rescinding the amended Regulation and restore the original Regulation No. 9. By the amended regulation by proceedings in BP 15/93, a concession was given to petitioners in the nature of incentive. The same was withdrawn by passing another Regulation. When the anamoly has been found out, Board thought of rescinding the amended Regulation and restore the original Regulation No. 9. By the amended regulation by proceedings in BP 15/93, a concession was given to petitioners in the nature of incentive. The same was withdrawn by passing another Regulation. It is in this background, we have to consider whether principle of promissory estoppel applies to the facts of this case. 32. H.W.R. Wade & C.F. Forsyth on Administrative Law (7th Edition) at page 268 of the book considered the basic principles of ‘Promissory Estoppel’, which reads thus, “The basic principle of estoppel is that a person who by some statement or representation of fact causes another to act to his detriment in reliance on the truth of it is not allowed to deny it later, even though it is wrong. Justice here prevails over truth. Estoppel is often described as a rule of evidence, but more correctly, it is a principle of law. As a principle of common law, it applies only to representations about past or present facts. But there is also an equitable principle of ‘promissory estoppel’ which can apply to public authorities.” What are the limitations in invoking principle of promissory estoppel was also considered by the learned authors. At page 270 of the book, learned authors have said thus, “In public law, the most obvious limitation on the doctrine of estoppel is that it cannot be invoked so as to give an authority powers which it does not in law possess. In other words, no estoppel can legitimate action which is ultra vires.” At page 271 it is further said that the principle of estoppel does not operate at the level of government policy. 33. The scope of promissory estoppel came up for consideration before the Honourable Supreme Court in the decision reported in 1991 1 S.C.C. 761 ( Vasant-kumar Radhakisan Vora v. Board of Trustees of the Port of Bombay ). In that case, their Lordships approved the decision of Motilal Padampat Sugar Mills case reported in 1979 2 SCC 409 , wherein it is held thus, “ there can be no promissory estoppel against the legislature in the exercise of its legislative functions nor can the government or public authority be debarred by promissory estoppel from enforcing a statutory prohibition. In that case, their Lordships approved the decision of Motilal Padampat Sugar Mills case reported in 1979 2 SCC 409 , wherein it is held thus, “ there can be no promissory estoppel against the legislature in the exercise of its legislative functions nor can the government or public authority be debarred by promissory estoppel from enforcing a statutory prohibition. It is equally true that promissory estoppel cannot be used to compel the government or a public authority to carry out a representation or promise which is contrary to law or which was outside the authority or power of the officer of the government or of the public authority to make. We may also point out that the doctrine of promissory estoppel being an equitable doctrine, it must yield when the equity so requires; if it can be shown by the government or public authority that having regard to the facts as they have transpired, it would be inequitable to hold the government or public authority to the promise or representation made by it, the court would not raise an equity in favour of the person to whom the promise or representation against the government or public authority.” And in para 18 of the Judgment, their Lordships further declared thus, “18. It is equally settled law that the promissory estoppel cannot be used to compel the government or a public authority to carry out a representation or promise which is prohibited by law or which was devoid of the authority or power of the officer of the government or the public authority to make. We may also point out that the doctrine of promissory estoppel being an equitable doctrine, it must yield place to the equity, if lar ger public interest so requires, and if it can be shown by the government or public authority, for having regard to the facts as they have transpired that it would be inequitable to hold the government or public authority to the promise or representation made bv it. The court on satisfaction would not, in those circumstances raise the equity in favour of the persons to whom a promise or representation is mask and enforce the promise or representation against government or the public authority. The court on satisfaction would not, in those circumstances raise the equity in favour of the persons to whom a promise or representation is mask and enforce the promise or representation against government or the public authority. Equally promissory estoppel should not be extended, though it may be founded on an express or implied promise stemmed from the conduct or representation bv an officer of the State or Public authority when it was obtained to play fraud on the Constitution and the enforcement would defeat or tend to defeat the constitutional goals . For instance, a right to reservation either under Article 15 (4) or 16 (4) in favour of the Scheduled Castes, Scheduled Tribes or backward classes was made with a view to ameliorate their status socially, economically and educationally so as to assimilate those sections into the mainstream of the society. The persons who do not belong to those classes, but produce a certificate to mask their social status and secure an appointment to an office or post under the state or public employment or admission into an educational institution maintained by the State or receiving aid from the State, on later investigation, though belated, was found that the certificate produced was false and the candidate was dismissed from the post or office or debarred or sent out from the institution or from the balance course of the study, the plea of promissory estoppel would always be found favour with the courts and being easily extended in favour of the candidate or party that played fraud on the Constitution. It would amount not only to putting a premium on the fraud on the Constitution, but also a denial to reserved candidate and the general candidate as well. Therefore, the plea of promissory estoppel should not be extended to such areas.” (Emphasis supplied) 34. In 1996 5 S.C.C. 468 (D.C.M. Limited v. Union of India), in para 6 of the Judgment, it is held thus, “ It is well-settled that the doctrine of promissory estoppel represents a principle evolved by equity to avoid injustice and, though commonly named promissory estoppel, it is neither in the realm of contract nor in the realm of estoppel. The basis of this doctrine is the inter-position of equity which has always proved to its form, stepped in to mitigate the rigour of strict law. The basis of this doctrine is the inter-position of equity which has always proved to its form, stepped in to mitigate the rigour of strict law. It is equally true that the doctrine of promissory estoppel is not limited in its application only to defence but it can al so find a cause of action. This doctrine is applicable against the Government in the exercise of its governmental public or executive functions and the doctrine of executive necessity or freedom of future executive action, cannot be invoked to defeat the applicability of this doctrine. It is further well-established that the doctrine of promissory estoppel must yield when the equity so requires. If it can be shown by the Government or public authority to the promise or representation made by it, the cou rt would not raise an equity in favour of the person to whom the promise or representation is made and enforce the promise or representation against the Government or public authority. The doctrine of promissory estoppel would be displaced in such a case because on the facts, equity would not require that the Government or public authority should be held bound by the promise or representation made by it.” 35. In 1997 7 S.C.C. 251 (Pawan Alloys & Castings Pvt. Ltd. v. U.P.S.E.B.) their Lordships followed the decision in Kasinka Trading v. Union of India reported in 1995 1 SCC 274 , wherein their Lordships, have considered the limitation of applicability of promissory estoppel, which reads thus, “11. The doctrine of promissory estoppel or equitable estoppel is well established in the administrative law of the country. To put it simply, the doctrine represents a principle evolved by equity to avoid injustice. The doctrine of promissory estoppel or equitable estoppel is well established in the administrative law of the country. To put it simply, the doctrine represents a principle evolved by equity to avoid injustice. The basis of the doctrine is that where any party has by his word or conduct made to the other party an unequivocal promise or representation by word or conduct, which is intended to create legal relations or effect a legal relationship to arise in the future, knowing as well as intending t hat the representation, assurance or the promise would be acted upon by the other party to whom it has been made and has, in fact, been so acted upon by the other party, the promise, assurance or representation should be binding on the party making it and that party should not be permitted to go back upon it, if it would be inequitable to allow him to do so, having regard to the dealings, which have taken place or are intended to take place between the parties. 12. It has been settled by this Court that the doctrine of promissory estoppel is applicable against the Government also particularly where it is necessary to prevent fraud or manifest injustice. The doctrine, however, cannot be pressed into aid to compel the Government or the public authority ‘to carry out a representation or promise which is contrary to law or which was outside the authority or power of the officer of the Government or of the public authority to make.’ There is preponderance of judici al opinion that to invoke the doctrine of promissory estoppel clear, sound and positive foundation must be laid in the petition itself by the party invoking the doctrine and that bald expressions, without any supporting material, to the effect that the doctrine is attracted because the party invoking the doctrine has altered its position relying on the assurance of the Government would not be sufficient to press into aid the doctrine. In our opinion, the doctrine of promissory estoppel cannot be invoked in the abstract and the courts are bound to consider all aspects including the results sought to be achieved and the public good at large, because while considering the applicability of the doctrine, the courts have to do equity and the fundamental principles of equity must for ever be present to the mind of the court, while considering the applicability of the doctrine, The doctrine must yield when the equity so demands if it can be shown having regard to the facts and circumstances of the case that it would be inequitable to hold the Government or the public authority to its promise, assurance or representation.” (Emphasis supplied) And finally in para 30 of the Judgment their Lordships held that one of the conditions for application of promissory estoppel hinges upon balance of equity or ‘public interest’.