Viewed from a different perspective, the failure of the United States to become a party to the Declaration of Paris proved advantageous, for in the Civil War, which broke out in 1861, the United States remained free of any international legal commitments regarding neutral rights vis-à-vis the major naval powers of the time. For the first time in its history, the United States was the preponderant belligerent naval power, and that freedom would permit it to pursue any course at sea calculated to increase the chances of victory. As a matter of fact, the United States did expand its belligerent rights during the war and did constrict those rights of neutrals that it had championed since the earliest days of the Republic.
Early in the war, Secretary of State William H. Seward informed the principal neutral powers that American policy toward their commerce would be governed by the second, third, and fourth articles of the Declaration of Paris. And the United States did, during the course of the war, respect the principles of "free ships make free goods" and the freedom from seizure of neutral goods (not contraband) in enemy ships. On blockade, however, the United States strayed far from its traditional position. It is true that Seward insisted that a blockade not maintained by an adequate force need not be respected and that every effort was made to station a sufficient number of vessels at the blockaded ports to prevent entry and exit. It is true, too, that the British government accepted the existence of an effective (and, hence, a legal) blockade and respected it. But it is also true that in an effort to make the blockade more effective, the United States indulged in some highly questionable practices that the British had used when a belligerent in the French revolutionary and Napoleonic wars (1793–1815) and against which the United States had protested vigorously. One, called the long-range blockade, was accomplished by "flying squadrons" of swift warships that patrolled the sea-lanes and intercepted neutral vessels far from a blockaded port, seizing them if there were grounds for believing their destination to be a blockaded port. Another was to place neutral ports (in Britain, the Bahamas, Mexico, and the West Indies) under surveillance and capture vessels as they left the protection of territorial waters, presumably for a port under blockade. In addition, Union warships took as prizes on the high seas neutral vessels coming from and going to neutral ports, on the ground that the ship and its cargo were ultimately destined for a blockaded port. American prize courts upheld the seizures, considering the voyage between the neutral port of origin and the blockaded port as one continuous, albeit broken, voyage. The doctrine was also applied to contraband. It was strange to find the United States applying the doctrine of continuous voyage, which had been so objectionable when practiced by the British in the wars against France.
In the matter of contraband, the United States did not publish an official list; but the secretary of the Treasury, in a circular sent to collectors of customs at several Southern ports where the blockade had been lifted, enumerated articles considered contraband and therefore banned from the ports. Among them were arms, munitions, and war supplies, as was to be expected. But the list also included naval stores and a host of other items, such as ardent spirits, corn, bullion, printing presses, coal, iron, lead, copper, tin, brass, telegraphic instruments, wire, and marine engines—and those were not to be expected. They flew in the face of the historic American resistance to an expanded contraband list.
Why the United States turned its back on history and tradition, and exchanged the role of champion of the rights of neutrals for that of defender of the rights of belligerents, can be explained only in terms of a sacrifice of principle for expediency. Winning the war was the overriding factor in determining the nation's policy. Nothing else mattered.