One of the most far-reaching of all Marshall's opinions on questions of international law was that which he delivered in the case of the schooner "Exchange," decided by the Supreme Court in 1812. In preparing this opinion he was, as he declared, compelled to explore "an unbeaten path, with few, if any, aids from precedents or written laws;" for the status of a foreign man-of-war in a friendly port had not then been defined, even by the publicists. The "Exchange" was an American vessel, which had been captured and confiscated by the French under the Rambouillet decree,--a decree which both the Executive and the Congress of the United States had declared to constitute a violation of the law of nations. She was afterwards converted by the French government into a man-of-war, and commissioned under the name of the "Balaou." In this character she entered a port of the United States, where she was libelled by the original American owners for restitution. Seasoning by analogy, Marshall, in a remarkably luminous opinion, held that the vessel, as a French man-of-war, was not subject to the jurisdiction of the ordinary tribunals; and his opinion forms the basis of the law on the subject at the present day. By this decision, the rightfulness or the wrongfulness of the capture and condemnation of the "Exchange" was left to be determined by the two governments as a political question. In this respect Marshall maintained, as between the different departments of government, when dealing with questions of foreign affairs, a distinction which he afterwards sedulously preserved, confining the jurisdiction of the courts to judicial questions. Thus he laid it down in the clearest terms that the recognition of national independence, or of belligerency, being in its nature a political act, belongs to the political branch of the government, and that in such matters the courts follow the political branch. Referring, on another occasion, to a similar question, he said: "In a controversy between two nations concerning national boundary, it is scarcely possible that the courts of either side should refuse to abide by the measures adopted by its own government.... If those departments which are entrusted with the foreign intercourse of the nation, which assert and maintain its interests against foreign powers have unequivocally asserted its rights of dominion over a country of which it is in possession, and which it claims under a treaty; if the legislature has acted on the construction thus asserted, it is not in its own courts that this construction is to be denied." (Foster _v_. Neilson).