THIS was an appeal from the Circuit Court of the United States for the District of California.
The case was one of collision between the American ship Sapphire and the French transport Euryale, which took place in the harbor of San Francisco on the morning of December 22, 1867, by which the Euryale was considerably damaged. A libel was filed in the District Court two days afterwards, in the name of the Emperor Napoleon III, then Emperor of the French, as owner of the Euryale, against the Sapphire. The claimants filed an answer, alleging, among other things, that the damage was occasioned by the fault of the Euryale. Depositions were taken, and the court decreed in favor of the libellant, and awarded him $15,000, the total amount claimed. The claimants appealed to the Circuit Court, which affirmed the decree. They then, in July, 1869, appealed to this court. In the summer of 1870, Napoleon III was deposed. The case came on to be argued here February 16, 1871. Three questions were raised:
1. The right of the Emperor of France to have brought suit in our courts.
2. Whether, if rightly brought, the suit had not become abated by the deposition of the Emperor Napoleon III.
3. The question of merits; one of fact, and depending upon evidence stated towards the conclusion of the opinion (see infra, pp. 169, 170), where the point is considered.
Mr. C. B. Gooderich, for the appellant:
1. The sovereign of a country, the public rights or property of which have been destroyed, or injured, by a citizen of another country, cannot maintain suit against such citizen, in the judicial tribunals of the country to which such citizen belongs, to recover compensation for the injury. The remedy, and the only remedy, of the foreign sovereign is by diplomatic correspondence and arrangement between the two countries. The repose of nations, and their intercourse with each other, cannot be maintained, if sovereign rights are to be ascertained and adjudicated by a suit, in the name of the foreign sovereign, against a private citizen by whom they may have been violated. 
The case before the court illustrates the propriety of the principle and reason upon which the position is taken. The claimants cannot call upon Napoleon, to answer interrogatories, upon oath, under the admiralty rule which requires libellants to answer. The owners of the Sapphire, in their answer, say that the collision was caused by the fault of the French transport. Admitting this to be true, still they cannot obtain a warrant for the arrest of a vessel belonging to the navy of France,  and which is in our harbor in the charge of an officer of the French navy.
There should in every proceeding be a mutuality of remedy. In the case of specific performance, whenever from personal incapacity, the nature of the contract, or any other cause, the contract is incapable of being performed, against one party, that party is equally incapable of enforcing it against the other, though its execution in the latter way might in itself be free from the difficulty attending its execution in the former.
The case of Prioleau v. United States and Andrew Johnson,  presents in its result difficulties attending a suit in the name of a foreign government, which can be surmounted only by holding that a foreign sovereign cannot maintain suit in the courts of another country, against its citizens, for the purpose of vindicating his sovereign rights. In the assertion of individual private rights he may have suit.
The cases cited say, that a foreign sovereign, by the institution of a suit, submits to the jurisdiction of the court divested of his sovereign rights; must answer to a cross-bill, upon oath; make discovery, or put some one forward, as party to the suit, who can. This shows that his sovereign rights cannot with propriety become the subject of a suit.
2. But supposing that the suit could yet be maintained if Napoleon III were now Emperor, it would seem certain that it cannot be continued, he being now deposed, and reduced to the state of a private person. The Euryale is a vessel of the French government; a government with which he has nothing whatever now to do; being banished and a fugitive.
3. [The counsel then discussed the question of fact.]
Mr. C. Cushing, contra (a brief of Mr. Melton Andrews being submitted on the merits), stated that suits had been maintained in Great Britain, in the name of the United States, within the last five years, in the following cases, he himself having been counsel in the same, namely: The Sumter (Admiralty), The Rappahannock (Admiralty), The Gibraltar (Admiralty), The Tallahassee (Admiralty), The Alexander (Admiralty), Prioleau (Chancery), Wagner (Chancery), Tait (Law), Gudgeon (Chancery), Blakely Company (Rolls), and in British America, in the case of Boyd and others (Chancery), and The Georgia (Admiralty).
Indeed the right of a government to sue in the courts of Great Britain is a right recognized from the time of Rolle's Abridgement (Temp. James I). 
The courts in England hold, indeed, that a sovereign cannot be forced into court by suit, and to that extent some of the cases cited on the other side go. But they admit that, if a foreign sovereign appears in court voluntarily as plaintiff, the defendant may then sue him by cross-bill or otherwise. That is not to deny his right to sue, but only to declare its consequences.
2. The right to sue having been in this case one in which the name of the late Emperor was used only as representing the government, survives his deposition. Substitution on the record of the name of any new government of France, is matter as of course.
3. [The counsel then discussed the question of fact.]
Mr. Justice BRADLEY delivered the opinion of the court.
^1 Duke of Brunswick v. The King of Hanover, 6 Beavan, 1; S.C.., 2 House of Lords Cases, N. S. 1; Hullet v. The King of Spain, 1 Dow & Clark, 169; S.C.., 1 Clark & Finelley, 333; Prioleau v. United States and Andrew Johnson, Law Reports, 2 Equity Cases, 659.
^2 Brown v. Duchesne, 19 Howard, 183.
^3 Law Reports, 2 Equity Cases, 659.
^4 Title 'Court de Admiralty,' E. 3; S.C.., 1 Rolle's Reports, 133.