RAMASWAMY, J.

1. Special leave granted.

2. This appeal under Article 136 arises against order dated September 16, 1988 of the High Court of Punjab and Haryana refusing to review the order dated August 11, 1988 made in Civil Revision No. 2439 of 1980 on its file. The facts leading to the decision are that the respondent Gobind Ram, the father of respondents/landlord laid the Suit No. 118/77 (initially numbered as O.S. No. 276 of 1975) on the file of Senior Sub-Judge for ejectment and recovery of arrears of rent and damages for use and occupation of the shop in Gurgaon, let out to the appellant/tenant. The suit was originally laid in Court of Sub-Judge, IIIrd Class, Gurgaon which was transferred later to Senior Sub-judge, Gurgaon, which was decreed ex parte on October 20, 1977. The application under Order IX Rule 13 CPC to set aside ex parte decree was dismissed on January 10, 1979 and was confirmed on appeal on August 17, 1979 and in revision by the High Court on October 15, 1979. When the landlord laid the execution application for ejectment the appellant objected under Section 47 of CPC contending that decree of civil court is nullity as the premises in question is governed by Haryana Urban (Control of Rent and Eviction) Act, 11 of 1973, for short the. The Controller under the is the competent forum regarding claims for ejectment on fulfillment of any of the conditions enumerated under Section 13 thereof. The civil court is divested of jurisdiction to take cognisance and passed a decree for ejectment of the appellant. That objection was overruled and on further revision the High Court dismissed the revision by order dated March 19, 1980. Simultaneously he also filed writ petition under Article 227 which was dismissed on September 30, 1988. This appeal is directed against that order of dismissal.

3. The contention raised by Shri S. P. Goyal, the learned senior counsel for the appellant is that by operation of Section 13 of thethe only authority to pass a decree of ejectment of the appellant tenant is the Controller under the and by necessary implication the jurisdiction of the civil court is ousted. The civil court lacked inherent jurisdiction to take cognizance of cause and to pass a decree. The decree is thus a nullity. The decree is thus a nullity. The challenge to a decree on the ground of nullity can be raised at any stage and even in execution. The court below have committed manifest error of law in not considering the legal question in its proper perspective. The shop consists of the original building belonging to the landlord, but a small part thereof in the front side was constructed on the municipal land. Tenancy of the building is governed by the special Act and, therefore, the decree of the civil court is a nullity and is inexecutable. Shri. Ashri, the learned counsel for the respondents refuted this contention. Firstly he argued that the leave application is barred by limitation. Secondly, he contended that the appellant had raised the plea of want of jurisdiction at the trial. Though he remained ex parte, the trial court considered the objection under issue Nos. 4 & 5 and overruled the objection. The decree became final; thereby the decree operates res judicata. He also further contends that the does not apply to the building in question. Under Section 3, municipal land is exempted from the provision of the and thereby the only forum to lay the action is civil court. The civil court having jurisdiction has validly granted the decree. The decree having been allowed to become final, it is not open to the appellant to ask the executing court to go behind the decree.

4. The question that emerges is whether the civil court lacked inherent jurisdiction to entertain the suit for ejectment of the appellant tenant and the decree so passed is a nullity. The Act was enacted with the object of controlling the increase of rent of building and rented lands situated within the limits of the urban areas and "the eviction of the tenants therefrom". Section 2(a) defines building which means any building or a part of a building let for any purpose whether being actually used for that purpose or not, including any land .... appurtenant to such building .... but does not include a room in a hotel, hostel or boarding house". Section 2(b) defines Controller as any person who is appointed by the State Government to perform the functions of a Controller under the. Landlord has been defined under Section 2 (c) and Section 2(f) defines rented lands to mean any land let separately for the purpose of being used principally for business or trade. Tenant has been defined under Section 2(h). Section 3 authorises the State Government by notification to exempt any particular building or rented land or any class of building or rented lands from the application of any or all the provisions of the. Section 13 contains the provisions for eviction of tenants, sub-section (1) thereof reads:

"13. Eviction of tenants. - (1) A tenant in possession of a building or a rented land shall not be evicted therefrom except in accordance with the provisions of this section."

5. The other provisions are not necessary. The sole ground raised by the landlord for eviction was that the appellant had committed default in the payment of rent and thereby had become liable for ejectment. Accordingly, he issued a notice under Section 106 of Transfer of Property Act determining the tenancy and laid this suit. Section 13 gives right to landlord to seek eviction of the tenant for default in payment of rent. The Act provides the protection of continued tenancy and remedy of ejectment for breach of covenants in the lease and other statutory grounds as provided. It provides that the remedy and the forum and the decree of ejectment passed by the Controller or the appellate authority or the revisional authority or confirmation thereof either in appeal or in revision is final under the. Thereby the exclusive jurisdiction to take cognizance of the cause of action of the tenant from a building or rented land situated in urban areas is governed by provisions of the and is exclusively to be dealt with under Section 13 of the. By necessary implication jurisdiction of the civil court under Section 9 of CPC is excluded. It is undoubtedly true that open land is a part of frontage of the shop and belongs to the municipality which the landlord had taken on lease from the municipality. As regards the municipality land, the landlord was lessee of the Municipal Committee. But on construction of building covering a portion of the municipal land the landlord becomes landlord and the appellant his tenant for the purposes of the. This view was held by the Full Bench of Punjab and Haryana High Court in Hari Prasad Gupta v. Jitender Kumar Kaushik ((1982) 84 Punj LR 150 : AIR 1982 P & H 165 : (1982) 1 Rent LR 337). We agree with this view. Thereby though there is a notification issued by the State Government exempting the lands belonging to Gurgaon municipality from the provisions of the, the building of the respondent does not get exempted from the provisions of the. It is the finding of the forums below that the shop in question stands mainly on the land and a small portion is located on the municipal land. Therefore, we are of the view that building was governed by the provisions of the and the exemption according by the Government under Section 3 was not attracted to the premises. In Sadhu Singh v. District Board, Gurdaspur ((1962) 64 Punj LR 1 : AIR 1962 Punj 204) the question was whether to the reconstructed building governed by the provisions of the East Punjab Urban Rent Restriction Act the exemption under Section 3 applied. It was held to be so by the Division Bench. But the present facts are different.

6. In Barraclough v. Brown (1897 AC 615 : 66 LJ QB 672 : 13 TLR 527) the Houses of Lords held that when a special statute gave a right and also provided a forum for adjudication of rights, remedy has to be sought only under the provisions of that Act and the common law of court has no jurisdiction.

7. In Doe d. Rochester (BP.) v. Bridges ((1831) 1 B & Ad 847, 859 : 109 ER 1001) the famous and oft quoted words of Lord Tenterdan, occur;

"Where an Act creates an obligation and enforces the performance in a specified manner, we take it to be a general rule that performance cannot be enforced in any other manner."

8. This statement of law was approved not only by Houses of Lords in several cases, but also by this court in Premier Automobiles Ltd v. K. S. Wadke ((1976) 1 SCC 496 [LQ/SC/1975/305] : 1976 SCC (L&S) 70 : (1976) 1 SCR 427 [LQ/SC/1975/305] ) where this Court was called upon to consider whether the civil court can decide a dispute squarely coming within the provisions of the Industrial Disputes Act. While considering that question, this Court laid down four propositions and third of them is relevant for consideration here. It is as follows : (SCC pp. 513-14, Par. 23)

"3. If the industrial dispute relates to the enforcement of a right or an obligation created under the, then the only remedy available to the suitor is to get an adjudication under the."

9. Thus on construction of relevant provisions of the light of the position in law it must be held that provisions of Section 13 of theapply to the building leased out to the appellant by the landlord and the Controller was the competent authority to pass a decree of ejectment against the appellant and the civil court lacked inherent jurisdiction to take cognizance of the cause and to pass a decree of ejectment therein. The next question is whether the impugned decree is nullity and whether plea can be raised in execution and further whether the decree in the suit does not operate as res judicata.

10. In Kiran Singh v. Chaman Paswan ((1955) 1 SCR 117 [LQ/SC/1954/68] : AIR 1954 SC 340 [LQ/SC/1954/68] ) the facts were that the appellants had undervalued the suit at Rs. 2950 and laid it in the Court of the Subordinate Judge, Monghyr for recovery of possession of the suit lands and mesne profits. The suit was dismissed and on appeal it was confirmed. In the second appeal in the High Court the Registry raised the objection as to the valuation of under Section 11. The value of the appeal was fixed at Rs. 9980. A contention then was raised by the plaintiff in the High Court that on account of the valuation fixed by the High Court the appeal against the decree of the court of the Subordinate Judge did not lie to the District Court, but to the High Court and on that account the decree of the District Court was nullity. Alternatively, it was contended that it caused prejudice to the appellant. In considering that contention at page 121, a four judge bench of this Court speaking through Venkatarama Ayyar, J. held that : (SCR p. 121)

"It is fundamental principle well established that a decree passed by the court without jurisdiction is a nullity, and that its invalidity could be set up whenever and wherever it is sought to be enforced or relied upon, even at the stage of execution and even in collateral proceedings. A defect of jurisdiction, whether it is pecuniary or territorial, or whether it is in respect of the subject matter of the action, strikes at the very authority of the court to pass any decree, and such a defect cannot be cured even by consent of parties. If the question now under consideration fell to be determined only on the application general principles governing the matter, there can be no doubt that the District Court of Monghyr was coram non judice, and that its judgment and decree would be nullities."

11. On merits it was held that since the appellant himself had invoked jurisdiction of the civil court with undervaluation, the objection as to jurisdiction was not available by operation of Section 99 of the Code and as to the territorial jurisdiction he was precluded by operation of Section 21 of CPC; and on such premise it was held that the decree of the District Court could not be treated as nullity and the person who invoked the jurisdiction cannot plead prejudice to himself by his own act.

12. This Court has held that it is a well established principle that a decree passed by a court without jurisdiction is a nullity and the plea can be set up whenever the decree is sought to be enforced or relied upon, and even at the stage of execution or in collateral proceedings.

13. In the case of Ferozi Lal Jain v. Man Mal (1970) 3 SCC 181 [LQ/SC/1970/127] : AIR 1970 SC 794 [LQ/SC/1970/127] the facts were that the appellant was the owner of a shop. One of the covenants under the lease was that the lessee respondent should not sub-let the shop. On the ground that the respondent had the sub-let shop, a suit was laid for eviction under Section 13 of the Delhi and Ajmer Rent Control Act, 1952. The matter was compromised and a compromise decree was passed. Twice time was given for delivery of the vacant possession by the respondent. On his failure to deliver vacant possession the appellant filed execution to recover possession. The tenant raised the objection that unless any one of the grounds prescribed under Section 13 of the Rent Control Act was satisfied, the decree even on compromise was a nullity and therefore, he could not be evicted. This court held that the order made did not show that it was satisfied that the sub-letting complained of had taken place, nor was there any material on record to show that it was satisfied. It is clear from the record that the court had proceeded solely on the basis of compromise arrived at between the parties. That being so there was hardly any doubt that court was competent to pass the impugned decree. Hence the decree under execution must be held to be a nullity. On that basis it was held that the objection could be raised even at the execution stage. Ultimately the decree was held to be void.

14. In Bahadur Singh v. Muni Subrat Dass ((1969) 2 SCR 432 [LQ/SC/1968/317] ) the decree under execution was made on the basis of an award and that it was held that the decree was passed in contravention of Section 13(1) of the Rent Control Act. Thereby the decree was held to be void and hence no execution could be levied on the basis of the void decree. A similar view was also taken by this Court in Kaushalya Devi v. K. L. Bansal ((1960) 1 SCC 59 : AIR 1970 SC 838 [LQ/SC/1968/383] ). This was also a case under the Delhi and Ajmer Rent Control Act was on the basis of a compromise. It was held that the decree passed on the basis of the award was in contravention of the Section 13(1) of theas the court had passed the decree without satisfying itself that any good ground of eviction existed. Therefore, the decree for delivery of possession was held to be a nullity and could not be executed. This also a decision by a bench of three judges speaking through Sikri, J. as he then was.

15. In Chandrika Misir v. Bhaiya Lal ((1973) 2 SCC 474 [LQ/SC/1973/218] ) Palekar, J. speaking for a bench of two judges held that a decree passed by the civil court in relation to the matters governed by the U.P. Zamindari Abolition and Land Reforms Rules, 1952 for possession was a nullity and in the appeal it was for the first time permitted to be raised in this Court and the decree was declared to be a nullity.

16. In Ledgard v. Bull ((1886) 13 IA 134 : (1886) 11 App Cas 648) the Privy Council laid down that where the original court in a suit was inherently lacking jurisdiction, and was incompetent to try the same, on its transfer by consent of the parties, to a court with jurisdiction such consent did not operate as a waiver of the plea for the want of jurisdiction.

17. In Barton v. Fincham ((1921) 2 KB 291, 299 : 90 LJ KB 451) it was held that

"Parties cannot by agreement give the courts jurisdiction which the legislature has enacted they are not to have the court cannot give effect to an agreement whether by way of compromise or otherwise, inconsistent with the provisions of the."

18. In Peachey Property Corporation Ltd v. Robinson ((1966) 2 All ER 981, 983 : (1967) 2 QB 543 (CA) Winn, Lord J. took the same view.

19. In Choudari Rama v. Qureshi Bee ((1983) 2 Andh LT 133 (AP)), one of us Ramaswamy, J. was called upon to consider the question on a set of similar facts. Therein the petitioner who died subsequently was protected under A.P. (Telangana Area) Tenancy and Agricultural Holdings) Act, 1950. The protected tenant was given possession in exercise of statutory power under Section 38-A of that Act. That was during the pendency of the suit for partition between the co-sharers. The tenant was impleaded co-nominee defendant of the suit. A preliminary decree for partition and the possession was passed. A final decree followed. The decree became final and execution was levied for possession. Objection was taken that since the tenant was protected under the, the decree was a nullity and could not be executed against the legal representatives. After considering the scope of the relevant provisions of the, it was held that the civil court cannot go into the legality or correctness of Ex. B-I issued by the Tehsildar. The revenue authorities constituted under that Act were competent to go into the validity thereof. Civil court inherently lacked jurisdiction and the decree of ejectment of the protected tenant from the lands covered by the protected tenancy was a nullity because of the provisions of Chapter IV of the. The plea can be set up even at the stage of execution, as was rightly done in that case. Otherwise it would have the effect of nullifying the operation of the statutory provisions in Chapter IV of the and deprive the protected tenant of his vested interest in the land created in his favour under the tenancy certificate (Ex. B-I). It was also held in Paragraph 64 that "Its validity can be assailed in the execution proceedings." We approve the view of the High Court.

20. In Mathura Prasad Bajoo Jaiswal v. Dossibai N. B. Jeejeebhoy ((1970) 1 SCC 613 [LQ/SC/1970/84] : (1970) 3 SCR 830 [LQ/SC/1970/84] ) the bench consisting of Shah, C.J., Hegde and Grover, JJ. was called upon to consider whether a decree passed without jurisdiction operates res judicata. The facts therein were that the respondent leased out the land for construction of a building to the appellant, which was duly constructed. The tenant applied for fixation of the standard rent. The civil court rejected the prayer holding that Bombay Rents, Hotel and Lodging House Rates Control Act, 1947 does not apply to the open land let out for construction. But later the High Court reversed the view that in another decision and held that the applied to the open land leased out. Relying upon that judgment, an application was again filed for fixation of standard rent of the premises. Objection was raised that the earlier rejection operated as res judicata. In that context, in negating the contention, this Court held that the doctrine of res judicata belongs to the domain of the procedure. It cannot be exalted to the status of a legislative direction between the parties so as to determine the question relating to the interpretation of enactment affecting the jurisdiction of a court finally between them, even though no question of fact or mixed question of law and fact relating to the right in dispute between the parties has been determine thereby. A decision of a competent court on a matter in issue may be res judicata in other proceedings between the same parties. The matter in issue may be an issue of fact. The fact decided by a competent court is final determination between the parties and cannot be reopened between them in another proceeding. The previous decision on a matter in issue is alone res judicata. The reasons for the decision are not res judicata. A matter in issue between the parties is the right claimed by one party and denied by the other. The claim of right from its very nature depends upon proofs of facts and application of the relevant law thereto. A pure question of law unrelated to the facts which give rise to a right, cannot be deemed to be a matter in issue. When it is said that a previous decision is res judicata, it is meant that the right claimed has been adjudicated upon and cannot again be placed in contest between the same parties. A previous decision a competent court on facts which are the foundation of the right and the relevant law applicable to the determination of the transactions which is the source of the right is res judicata. A previous decision on a matter in issue is a composite decision; the decision of law cannot be dissociated from the decision on facts on which the right is founded. A decision on an issue of law will be res judicata in a subsequent proceeding if it be the same as in the previous proceeding, but not when the cause of action is different, nor when the law has since the earlier decision been altered by a competent authority, nor when the decision relates to the jurisdiction of the court to try the earlier suit nor when the earlier decision declares the valid a transaction which is prohibited by law : (SCC pp. 618 - 19, paras 9 and 10)"A question of jurisdiction of the court, or procedure, or pure question of law unrelated to the right of the parties to previous suit, is not res judicata in the subsequent suit. Rankin, C.J., observed that in Tarini Charan Bhattacharjee case (Tarini Charan Bhattacharjee v. Kedar Nath Haldar, ILR 56 Cal 723 [LQ/CalHC/1928/318] : AIR 1928 Cal 777 [LQ/CalHC/1928/318] )."

"The object of the doctrine of res judicata is not to fasten upon parties special principles of law as applicable to them inter se, but to ascertain their rights and the facts upon which these rights directly and substantially depend; and to prevent this ascertainment from becoming nugatory or precluding the parties from reopening or recontesting that which has been finally decided".

A question relating to the jurisdiction of a court cannot be deemed to have been finally determined by an erroneous decision of the court by an erroneous interpretation of the statute the court holds that it has no jurisdiction, the question would not, in our judgment, operate as res judicata. Similarly by an erroneous decision if the court assumes jurisdiction which it does not possess under the statute, the question cannot operate as res judicata between the same parties, whether the cause of action in the subsequent litigation is the same or otherwise."

21. In that case it was held that since it relates to the jurisdiction of the court as per law declared by the legislature, it does not operate as res judicata.

22. In Vasudev Dhanjibhai Modi v. Rajabhai Abdul Rehman ((1970) 1 SCC 670 [LQ/SC/1970/148] ) a bench of three judges of this Court consisting of Shah, J., as he then was, Hegde and Grover, JJ., was considering the question of nullity of a decree. The facts therein were that the appellant, owner of the plot of land, leased out the same to the respondent at an annual rental of Rs. 411. The suit was dismissed and on appeal it was reversed and suit was decreed. On revision it was confirmed by the High Court. Special leave petition filed in this Court was also dismissed. In the execution of the contention was raised that the Small Causes Court has no jurisdiction to entertain the suit. It was contended that the decree was nullity on the ground that Bombay Rents, Hotel and Lodging House Rates (Control) Act 57 of 1947 applied to the facts in that case. In that context Shah, J., as he then was, speaking for the court held that challenge to a decree which is nullity can be raised at any time, but the court executing the decree cannot go behind the decree between the parties or on their representation it cannot entertain any objection that the decree was incorrect in law or on facts, unless it is set aside by an appropriate proceeding in appeal or revision. A decree even if it be erroneous is still binding between the parties. In that context it was held that the question whether the Court of Small Causes had jurisdiction to entertain the suit depended upon the interpretation of the terms of the agreement of lease, and the use to which the land was put at the date of the grant of the lease. These questions cannot be permitted to be raised in an execution proceeding so as to displace the jurisdiction of the court which passed the decree. It was further held that for the purpose of determining whether the court which passed the decree had jurisdiction to try the suit, it is necessary to determine facts are relevant to the issue on which the question depends, and the objection does not appear on the face of the record, the executing court cannot enter upon an enquiry into those facts. It is seen that on the facts in that case it is for the first time the executing court is to adjudicate upon the terms of the lease whether the Court of Small Causes has jurisdiction to entertain that suit. It is not a case of interpretation of the statutory provisions of inherent lack of jurisdiction. It is already seen that in fact for the first time this Court in Chandrika Misir case ((1973) 2 SCC 474 [LQ/SC/1973/218] ) had to go into the statutory provisions though no case in that regard had been set up in the courts below and held that the civil court lacked inherent jurisdiction to pass the decree. Therefore, the ratio in this case is not in conflict with the view taken by this Court.

23. It is no doubt true that in Seth Hiralal Patni v. Kali Nath ((1962) 2 SCR 747 [LQ/SC/1961/241] : AIR 1962 SC 199 [LQ/SC/1961/241] ) the facts were that the suit was instituted on the original side of the Bombay High Court against the appellant for recovery of certain arrears out of transactions taking place at Agra. The dispute was referred to arbitration. The arbitrator gave his award in favour of the respondent which was upheld on appeal by the High Court. In execution proceedings an objection was raised by the appellant that the Bombay High Court has no jurisdiction to entertain the suit to make the award a decree of the court as no part of the cause of action had arisen within its territorial jurisdiction. Therefore, the decree was without jurisdiction. It was held that since the parties had agreed to refer the matter to arbitration through court, which had jurisdiction, he would be deemed to have waived the objection as to the territorial jurisdiction of the court. Therefore, it is not a nullity and the appellant was held to be stopped from challenging the jurisdiction of the Bombay High Court. The ratio therein does not apply to the facts of this case.

24. The case of Phool Chand Sharma v. Chandra Shanker Pathak ((1963) Supp 2 SCR 828 : AIR 1964 SC 782 [LQ/SC/1962/416] ) also does not held the respondent. It was a case where the suit was decreed and possession was taken thereunder. On appeal by the respondent it was dismissed. On second appeal before the Board of Revenue the matter was compromised, whereunder Ramprasad was recognised as a tenant of the land in dispute and the order of eviction was thus nullified. When he made an application under Section 144 CPC for restitution it was revised by the tenants subsequently inducted on the ground that the respondent was inducted as tenant by the decree-holder, and the decree does not bind them. This was upheld by the trial court and on appeal. A writ petition was also dismissed on merits. The decree became final. The order of the High Court under Article 227 became final. Then against the order of the Board of Revenue an appeal under Article 136 was filed in this Court. A preliminary objection was raised that the decision of the High Court under Article 227 operated as res judicata. In that context it was held by this Court that the appeal was barred by res judicata as the decision of the High Court was on merits and would bind the parties unless it was modified or reversed in appeal or by other appropriate proceedings. The facts are clearly distinguishable.

25. The case of Mohanlal Goenka v. Benoy Krishna Mukherjee (1953 SCR 377 [LQ/SC/1952/88] : AIR 1953 SC 65 [LQ/SC/1952/88] ) is also of little assistance to the respondent. The decree passed by Calcutta High Court on its original side was transferred for execution to the Court of Subordinate Judge of Asansol with proper certified copy of the decree and order of transmission. The execution application was dismissed for default and a certificate was sent under Section 41 CPC stating that the execution case was dismissed for default without transmitting the decree or covering letter sent by the High Court. The decree holder again applied for the execution. It was accordingly executed. Then an application to set aside the sale was made under Order XXI Rule 90 CPC on the ground that decree is a nullity and the court has no jurisdiction to execute the decree. While negating the contention it was held that since the decree sent was not transmitted it would be regarded as a fresh application for execution and, therefore, the executing court had jurisdiction and the decree was not nullity. That case is also not one of the inherent lack of jurisdiction.

26. Thus it is settled law that normally a decree passed by a court of competent jurisdiction, after adjudication on merits of the rights of the parties, operates as res judicata in a subsequent suit or proceedings and binds the parties or the persons claiming right, title or interest from the parties. Its validity should be assailed only in an appeal or revision as the case may be. In subsequent proceedings its validity cannot be questioned. A decree passed by a court without jurisdiction over the subject matter or on other grounds which goes to the root of its exercise or jurisdiction, lacks inherent jurisdiction. It is a coram non judice. A decree passed by such a court is a nullity and is non est. Its validity can be set up whenever it is sought to be enforced or is acted upon as a foundation for right, even at the stage of execution or in collateral proceedings. The defect of jurisdiction strikes at the authority of the court to pass a decree which cannot be cured by consent or waiver of the party. If the court has jurisdiction but there is defect in its exercise which does not go to the root of its authority, such a defect like pecuniary or territorial could be waived by the party. They could be corrected by way of appropriate plea at its inception or in appellate or revisional forums, provided law permits. The doctrine or res judicata under Section 11 CPC is founded on public policy. An issue of fact or law or mixed question of fact and law, which are in issue in an earlier suit or might and ought to be raised between the same parties or person claiming under them and was adjudicated or allowed uncontested becomes final and binds the parties or persons claiming under them. Thus the decision of a competent court over the matter in issue may operate as re judicata in subsequent suit or proceedings or in other proceedings between the same parties and those claiming under them. But the question relating to the interpretation of statute touching the jurisdiction of a court unrelated to questions of fact or law mixed questions does not operate as rest judicata even between the parties or persons claiming under them. The reason is obvious; appear question of law unrelated to facts which are the basis or foundation of a right, cannot be deemed to be a matter in issue. The principle of res judicata is a facet of procedure but not of substantive law. The decision of any issue of law founded on fact in issue would operate as res judicata. But when the law has since the earlier decision been altered by a competent authority or when the earlier decision declares a transaction to be valid despite prohibition by law it does not operate as res judicata. Thus a question of jurisdiction of a court or a procedure or a pure question of law unrelated to the right of the parties founded purely on question of fact in the previous suit, is not res judicata in the subsequent suit. A question relating to jurisdiction of the court or interpretation of provisions of statute cannot be deemed to have been finally determined by an erroneous decision of a court. Therefore, the doctrine of res judicata does not apply to case of decree of nullity. If the court inherently lacks jurisdiction consent cannot confer jurisdiction. Where certain statutory rights in a welfare legislation are created, the doctrine of waiver also does not apply to case of decree where the court inherently lacks jurisdiction27 In the light of this position in law the question for determination is whether the impugned decree of the civil court can be assailed by the appellant in execution. It is already held that it is the controller under the that the exclusive jurisdiction to order ejectment of a tenant from a building in the urban area leased out by the landlord. Thereby the civil court inherently lacks jurisdiction to enter the suit and passed a decree of ejectment. Therefore though the decree was passed and the jurisdiction of the court was gone into in issue Nos. 4 and 5 at the ex parte trial, the decree thereunder is a nullity, and does not bind the appellant. Therefore, it does not operate as a res judicata. The courts below have committed grave error of law in holding the decree of the suit operated as res judicata and the appellant cannot raise the same point at the execution.

28 It is seen from the dates mentioned that there is no delay in filling the leave application. The leave application was filed within the limitation from the date of original order of dismissal of the revision or on a later date dismissing the review application. It is true that the writ petition was filed against the order in revision, but it does not preclude the appellant to contest its invalidity in the appeal under Article 136. The decree was executed pending the special leave petition. This court would relieve the party from injustice in exercise of power under Article 136 of the Constitution when this Court noticed grave miscarriage of justice. It is always open to the appellant to take aid of section 144 CPC for restitution. Therefore, merely because the decree has been executed, on the facts when we find that decree is a nullity, we cannot decline to exercise our power under Article 136 of set at nought illegal orders under a decree of nullity. The appeal is accordingly allowed. But in the circumstances parties are directed to bear their own costs.