1 Opinion of the Court. cording to its conception of its own interests. Each State. has the unfettered right at any time to repeal its legislation. Each State is competent to construe and apply its legislation in the cases that arise within its jurisdiction. If it be assumed that the statutes of the two States have been enacted with a view to reciprocity in operation, nothing is shown which can be taken to alter their essential character as mere legislation and to create an obligation which either State is entitled to enforce as against the other in a court of justice. The suggestion that residents of Massachusetts are entitled to the immunity offered by the Missouri statute is unavailing, as Massachusetts may not invoke our jurisdiction for the benefit of such individuals. Oklahoma v. Atchison, T. & S. F. Ry. Co., 220 U. S. 277, 286; Oklahoma v. Cook, 304 U. S. 387, 394. Nor does the nature of the suit as one to obtain a declaratory judgment aid the complainant. To support jurisdiction to give such relief, there must still be a controversy in the constitutional sense (Aetna Life Insurance Co. v. Haworth, 300 U. S. 227, 240, 241) and as between the two States there is no such controversy here. Second.-Complainant urges that jurisdiction may be sustained in the view that the proposed bill of complaint presents a controversy between Massachusetts and citizens of Missouri. The bill is not aptly framed so as to present such a controversy independently of a controversy between the States. The bill expressly states the issues presented as being (a) whether Massachusetts or Missouri has exclusive jurisdiction over the transfers in trust so as to have the taxing power, and (b) secondarily, whether the State having such jurisdiction can constitutionally reach one of the trusts in which the settlor reserved no right of revocation. And the specific relief sought is that the Court may determine which State has the jurisdiction to tax and may award that Opinion of the Court. 308 U.S. jurisdiction to Massachusetts as against Missouri. If the gravamen of the proposed bill is deemed to be an assertion of a controversy between the States, jurisdiction to entertain the bill cannot be supported in the absence of the showing of such a controversy. Missouri cannot be brought into court by the expedient of making its citizens parties to a suit otherwise not maintainable , against the State. With respect to the second ground of invoking jurisdiction, as an independent ground, we are virtually asked to disregard the stated objective of the proposed bill, to treat it as amended so as to expunge claims against Missouri and to confine it to claims against the trustees; to consider the bill as no longer asking a declaratory judgment as to which State has power to tax, as not seeking relief in this Court "sitting as a court of equity," but, in the light of the general prayer for other relief, as presenting a simple action against the trustees to recover the amount of the tax claimed to be due Massachusetts irrespective of any claim of Missouri. If it be possible to consider the proposed bill as thus stripped of its abortive allegations against Missouri and as presenting a cause of action so distinct from that primarily relied upon, still the invocation of our jurisdiction must fail. In the exercise of our original jurisdiction so as truly to fulfill the constitutional purpose we not only must look to the nature of the interest of the complaining State the essential quality of the right asserted-but we must also inquire whether recourse to that jurisdiction in an action by a State merely to recover money alleged to be due from citizens of other States is necessary for the State's protection. In Oklahoma v. Cook, supra, we called attention to the enormous burden which would be imposed upon this Court if by taking title to assets of insolvent state institutions, including claims against citizens of other States, a State could demand access to the origi 1 Opinion of the Court. nal jurisdiction of this Court to enforce such claims. To open this Court to actions by States to recover taxes claimed to be payable by citizens of other States, in the absence of facts showing the necessity for such intervention, would be to assume a burden which the grant of original jurisdiction cannot be regarded as compelling this Court to assume and which might seriously interfere with the discharge by this Court of its duty in deciding the cases and controversies appropriately brought before it. We have observed that the broad statement that a court having jurisdiction must exercise it (see Cohens v. Virginia, 6 Wheat. 264, 404) is not universally true but has been qualified in certain cases where the federal courts may, in their discretion, properly withhold the exercise of the jurisdiction conferred upon them where there is no want of another suitable forum. Canada Malting Co. v. Paterson Co., 285 U. S. 413, 422; Rogers v. Guaranty Trust Co., 288 U. S. 123, 130, 131. Grounds for justifying such a qualification have been found in "considerations of convenience, efficiency and justice" applicable to particular classes of cases. Rogers v. Guaranty Trust Co., supra. Reasons not less cogent point to the need of the exercise of a sound discretion in order to protect this Court from an abuse of the opportunity to resort to its original jurisdiction in the enforcement by States of claims against citizens of other States. In this instance it does not appear that Massachusetts is without a proper and adequate remedy. Clause 2 of § 2 of Article III merely distributes the jurisdiction conferred by clause one. Louisiana v. Texas, 176 U. S. 1, 16; Monaco v. Mississippi, 292 U. S. 313, 321. The original jurisdiction of this Court, in cases where a State is a party, "refers to those cases in which, according to the grant of power made in the preceding clause, jurisdiction might be exercised in consequence of the character of the party, and an original suit might be instituted in any of Opinion of the Court. 308 U.S. the federal Courts; not to those cases in which an original suit might not be instituted in a federal Court." Cohens v. Virginia, supra, pp. 398, 399. With respect to the character of the claim now urged, we are not advised that Missouri would close its courts to a civil action brought by Massachusetts to recover the tax alleged to be due from the trustees. The Attorney General of Missouri at this bar asserts the contrary. He says that "it would seem that Massachusetts should be able to bring a suit against the trustees for the collection of its taxes in either a Missouri state court or in a federal district court in Missouri" and that "such a suit would be of a civil nature and would present a justiciable case or controversy." We have said that the objection that the courts in one State will not entertain a suit to recover taxes due to another or upon a judgment for such taxes, is not rightly addressed to any want of judicial power in courts which are authorized to entertain civil suits at law. It goes "not to the jurisdiction but to the merits," and raises a question which district courts are competent to decide. Milwaukee County v. M. E. White Co., 296 U. S. 268, 272. The motion for leave to file the proposed bill of complaint is denied. Motion denied. MR. JUSTICE BUTLER took no part in the consideration and decision of this case. Argument for Petitioner. PITTMAN, CLERK OF THE SUPERIOR COURT OF BALTIMORE, v. HOME OWNERS' LOAN CORP. CERTIORARI TO THE COURT OF APPEALS OF MARYLAND. No. 10. Argued October 12, 13, 1939-Decided November 6, 1939. 1. The Maryland tax on mortgages, graded according to the amount of the loan secured and imposed, in addition to the ordinary registration fee as a condition to the recordation of the instrument, can not be applied to a mortgage tendered for record by the Home Owners' Loan Corporation and securing one of its loans, in view of the provisions of the Home Owners' Loan Act which declare the Corporation to be an instrumentality of the United States and that its loans shall be exempt from all state and municipal taxes. Federal Land Bank v. Crosland, 261 U. S. 374. P. 29. 2. Assuming that the creation of the Home Owners' Loan Corporation was a constitutional exercise of the power of Congress, the activities of the Corporation through which the Government lawfully acts must be regarded as governmental functions and entitled to whatever immunity attaches to those functions when performed by the Government itself through its departments. P. 32. The power of Congress to create a corporation to facilitate the performance of governmental functions implies a power to protect the operations thus validly authorized, which comes within the range of the express power conferred by Const. Art. I, § 8, cl. 18, to make all laws necessary and proper for carrying into execution all powers vested by the Constitution in the Government. In the exercise of this power to protect, Congress has the dominant authority which necessarily inheres in its action within the national field. 175 Md. 512; 2 A. 2d 689, affirmed. CERTIORARI, 306 U. S. 628, to review a judgment affirming the issuance of a mandamus by Baltimore City Court requiring the Clerk of the Superior Court of Baltimore to record a mortgage. Messrs. H. Vernon Eney, Assistant Attorney General of Maryland, and William C. Walsh, Attorney General, |