It is not, however, by any means essential to Marshall's pre-eminence as a judge, to show that his numerous opinions are altogether free from error or inconsistency. In one interesting series of cases, relating to the power of a nation to enforce prohibitions of commerce by the seizure of foreign vessels outside territorial waters, the views which he originally expressed in favor of the existence of such a right appear to have undergone a marked, if not radical, change, in favor of the wise and salutary exemption of ships from visitation and search on the high seas in time of peace (Rose _v_. Himely),--a principle which he affirmed on more than one occasion (The Antelope). In the reasoning of another case, though not in its result, we may perhaps discern traces of the preconceptions formed by the advocate in the argument concerning the British debts. This was the case of Brown _v_. United States, which involved the question of the confiscability of the private property of an enemy on land, by judicial proceedings, in the absence of an Act of Congress expressly authorizing such proceedings. On the theory that war renders all property of the enemy liable to confiscation, Mr. Justice Story, with the concurrence of one other member of the Court, maintained that the Act of Congress declaring war of itself gave ample authority for the purpose. The majority held otherwise, and Marshall delivered the opinion. Referring to the practice of nations and the writings of publicists, he declared that, according to "the modern rule," "tangible property belonging to an enemy and found in the country at the commencement of war, ought not to be immediately confiscated;" that "this rule" seemed to be "totally incompatible with the idea that war does of itself vest the property in the belligerent government;" and, consequently, that the declaration of war did not authorize the confiscation. Since effect was thus given to the modern usage of nations, it was unnecessary to declare, as he did in the course of his opinion, that "war gives to the sovereign full right to take the persons and confiscate the property of the enemy, wherever found," and that the "mitigations of this rigid rule, which the humane and wise policy of modern times has introduced into practice," though they "will more or less affect the exercise of this right," "cannot impair the right itself." Nor were the two declarations quite consistent. The supposition that usage may render unlawful the exercise of a right, but cannot impair the right itself, is at variance with sound theory. Between the effect of usage on rights, and on the exercise of rights, the law draws no precise distinction. A right derived from custom acquires no immutability or immunity from the fact that the practices out of which it grew were ancient and barbarous. We may therefore ascribe the dictum in question to the influence of preconceptions, and turn for the true theory of the law to an opinion of the same great judge, delivered twenty years later, in which he denied the right of the conqueror to confiscate private property, on the ground that it would violate "the modern usage of nations, which has become law" (U.S. _v_. Percheman).