delivered the opinion of the court.
These are petitions for prohibition to prevent District Courts'of the United States from exercising jurisdiction of proceedings in rem for collisions that occurred while the vessels libeled were owned, absolutely or pro hac vice, by the United States, and employed in the public service.. The questions arising' in the three cases are so nearly the same that they can be dealt with -together.
*430The Western Maid was and.is the property of the United States. On January 10,1919, she was allocated by the United States Shipping Board to the War Department for service as a transport. She had been loaded with foodstuffs for the relief of the civilian population of Europe, to be delivered on. arrival at Falmouth, England, to the order of the Food Administration Grain Corporation, the consignor, Américan Embassy, London, care of the Chief Quartermaster, American Expeditionary Forces, France; subject to the direction of Mr. Hoover. If it should prove impracticable to reship or redirect to the territories lately held by the Central Empires, Mr. ■Hoover was to resell to the Allied Governments or to the Belgian Relief; the foodstuffs to be paid for by the buyer. The vessel was manned by á navy crew. Later on the same day, January 10, 1919, in New York harbor, the collision' occurred. On March 20, 1919, the vessel was delivered' to the United States Shipping Board. The libel was filed on November 8, 1919 Act of September 7, 1916, c. 451, § 9, 39 Stat. 728, 730. The Lake Monroe, 250 U. S. 246. On February 20, 1920, the Government moved that it be dismissed for. want .of jurisdiction. The District Court overruled the motion.. On April 11, 1921, the Attorney General moved for leave to file the present petition in this Court. Leave was granted and the case has been heard.
,The Liberty was a pilot boat let to the United States on the bare-boat basis at a nominal rate of hire. She had been manned by a crew from the United States Navy and commissioned as a naval dispatch-boat, and was émployed t.o serve military needs-in war service. The collision took place on December 24,1917, while she was so employed, in Boston Harbor. Afterwards the vessel was redelivered to the owners and still later, on February 5, 1921, the suit now in question was brought against- her. On February 14, under the Act of March 9, 1920, c. 95, § 4, 41 Stat. 525, *431the United States filed a suggestion of its interest, and also set up the above facts. The District Court held that they constituted no defence and this petition was brought by the Attorney General along with that last mentioned.
The Steamship Carolinian had been chartered to the United States upon a .bare-boat charter, and had been assigned to the War Department, by which she was employed as an army transport and furnished with an army crew. While she was so employed the collision took place in the harbor of Brest, France, on February 15, 1918. Afterwards the Carolinian was returned to the owners, and she was employed solely as a merchant vessel on July 9, 1920, when the suit in question was begun, under which -the vessel was seized. .In the same month' the United States filed a suggestion of interest, and on January 6, 1921, set up the foregoing facts and prayed that the libel be dismissed. The District Court maintained its jurisdiction and this petition' was brought by the Attorney General along with the other two. 270 Fed. 1011.
It may be -assumed that each of these vessels might have been libeled for maritime torts committed after the redelivery that we have mentioned. But the Act of September 7, 1916, c. 451, § 9, does not create a liability on the part of the United States, retrospectively, where one did not exist before. Neither, in our opinion, is such a. liability created by the Act of March 9, 1920, c. 95, § 4, authorizing, the United States to assume the defence in suits like these. It is not required- to abandon any defence that otherwise would be good. It appears to us plain that before the passage of these acts neither the United States nor the vessels in the hands of the United States were liable to be sued for these alleged maritime torts. The Liberty and the Carolinian were employed for public and government purposes, and were owned pro hac vice by the United States. It is suggested that the Western Maid was a merchant vessel at the time , of the *432collision, but the fact that the food was to be paid for and the other details adverted to in argument cannot disguise the obvious truth, that she was engaged in a public service that was one of the constituents of our activity in the war and its sequel and that had no more to do with ordinary merchandizing than if she had carried a regiment of troops. The only question really open to debate is whether a liability attached to the ships which although dormant while the United States was in possession became enforcible as soon as the vessels came into hands that could be sued.
In deciding this question we must realize that however ancient may be the traditions of maritime law, however diverse the sources from which it has been drawn, it derives its whole and only power in this- country from its haying been accepted and adopted by the United States. There is no mystic over-law to which even the United States must bow. When a case is said to be governed by foreign law or by general maritime law that-is only a short way of saying that for this.purpose, the sovereign power takes up a rule suggested from without and makes it part of its own rules. The Lottawanna, 21 Wall. 558, 571, 572. Dalrymple v. Dalrymple, 2 Hagg. Cons. 54, 58, 59. Dicey, Conflict of Laws, 2d ed., 6, 7. Also .we must realize that the authority that makes the law is itself superior to it, and that if it consents to apply to itself the rules that it applies to others the consent is free and may be withheld. The sovereign does not create justice in an ethical sense, to be sure, and there may be cases in which it would, not dare to deny that justice for fear of war or revolution. Sovereignty is a question of power, and no human power is unlimited. Carino v. Insular Government of the Philippine Islands, 212 U. S. 449, 458. But. from the necessary point of view of the sovereign and its organs whatever is enforced by it as law is enforced as the *433expression of its will. Kawananakoa v. Polyblank, 205 U. S. 349, 353.
The United States has not consented to be sued for torts, and therefore it cannot be said that in a legal sense the United States has been guilty of a tort. For a tort is a tórt in a legal sense only because the law has made it so. If then we imagine the sovereign power announcing' the system of its laws in a single voice it is hard to conceive it as declaring that while it does not recognize the possi-. bility of its acts being a legal wrong and while its immunity from such an imputation of course extends to its property, at least when employed in carrying on the operations of the Government, — specifically appropriated to national objects, in the language of Buchanan v. Alexander, 4 How. 20,—yet if that property passes into other hands, perhaps of an innocent purchaser, it may be seized upon a claim that had no existence before. It may be said that the persons who actually did the act complained of may or might be sued and that the ship for this purpose is regarded- as a person. But that is a fiction not a fact and as a fiction is the creation of the law. It' would be a a strange thing if the law created a fiction to accomplish the result supposed. It is totally immaterial that in dealing with private wrongs the fiction, however originated, is in force. See Liverpool, Brazil & River Plate Steam Navigation Co. v. Brooklyn Eastern District Terminal, 251 U. S. 48, 53. The personality of a public vessel is merged in .that of the sovereign. The Fidelity, 16 Blatchf. 569, 573. Ex parte State of New York, No. 2, 256 U. S. 503.
But it is said that the decisions have recognized that an obligation is created in the case before us. Legal obligations that exist but cannot be enforced are ghosts that are seen in the law but that are elusive to the grasp. The leading authority relied upon is The Siren, 7 Wall. 152 *434The ground of that decision was that when the United States came into court to enforce a claim it would be assumed to submit to just claims of third persons in respect of the same subject-matter. 7 Wall. 154. Carr v. United States, 98 U. S. 433, 438. In reaching its result the Court spoke- of such claims as unenforcible liens,- but that was little more than a mode of expressing the consent of the sovereign power to see full justice done in such circumstances. It would have been just as effective and more accurate to speak of the claims as ethical only, but recognized in the interest of justice when the sovereign came into court. They were treated in this way by Dr. Lushington in The Athol, 1 Wm. Rob. 374, 382. Further distinctions have been taken that need not be adverted to here. There was nothing decided in Workman v. New York City, 179 U. S. 552, that is contrary to our conclusion, which, on the other hand, is favored by The Fidelity, 16 Blatchf. 569, 573, and Ex parte State of New York, No. 1, 256 U. S. 490, and Ex parte State of New York, No. 2, 256 U. S. 503; The last cited decisions also show that a prohibition may be. granted in a case like this. See The Ira M. Hedges, 218 U. S. 264, 270.
Rule absolute for writs of prohibition.
Mr. Justice McReynolds did not. hear the argument in this case and took no part in the decision.