Contraband (law Lat. contra and oannum, contrary to an edict, proclamation, or treaty), a term used to designate goods exported from or imported into a country in violation of its laws. Contraband of war, in international law, applies to goods which neutrals are prohibited from carrying during war to either of the belligerent parties. Whatever is directly of use for war, and for that only, as arms and ammunition, would of course be contraband; but articles which may be of use either in peace or war will be subject to a varying rule according to the existing circumstances. Thus, provisions may ordinarily be carried by a neutral to a belligerent without being deemed contraband; yet, in the case of a blockade of a town with the expectation of reducing it by famine, a neutral could not lawfully furnish provisions to the besieged party, as it would be giving means of assistance against one of the legitimate operations of war. Naval stores and materials for building or furnishing vessels of war are contraband by the modern law of nations; formerly they were so regarded only in a naval war, but at the present day, naval operations being more or less incident to every war, the rule has become general that the furnishing such materials to a belligerent is unlawful.

It has been a question whether, if the materials are not exclusively applicable to the building or furnishing of war vessels, they would necessarily be contraband. It has been held in the English admiralty courts that they would be; but in the French council of prizes it was decided in 1807 that ordinary ship timber, adapted to the building of merchant vessels as well as vessels of war, carried to an enemy's port, was not per se to be deemed contraband. In the war between England and France which commenced near the close of the last century, it was attempted by both nations to enforce a stricter rule against neutral powers than had been maintained before that time by any nation of modern Europe. The national convention of France in 1793 decreed that neutral vessels laden with provisions, destined to an enemy's port, should be seized and carried to France, which was followed by an order of the English government to detain all neutral vessels bound for France having corn, meal, or flour, on board.

The ground upon which England justified this detention was, that the depriving the enemy of the supplies necessary for her population was one of the means relied upon for reducing her to accept reasonable terms of peace; and that, under this plan of operations, all provisions destined for any port of France were contraband. This claim was resisted by the government of the United States, who insisted that provisions were never contraband, except when destined to a place which was actually invested. The courts of the United States have, however, since that time admitted that provisions intended for the use of the army or navy of the enemy, or destined to his posts of military or naval equipment, should be deemed contraband; and the decisions in the English admiralty courts substantially limit the rule as to provisions being contraband to the cases above specified; so that the courts of both countries are in conformity with each other, and the claim made by the English government in 1793 seems to be abandoned, or at all events is not likely ever to be reasserted, unless in a contest as desperate as that in which she was then engaged.

Confiscation is the penalty upon seizure of contraband goods, except in the case of provisions, as to which the practice has been substituted of taking them at a reasonable price instead of enforcing forfeiture. It is understood that confiscation of the goods is not a just ground of complaint on the part of the neutral power, and is not the subject of reclamation. So, on the other hand, the neutral power is not chargeable with a breach of neutrality if it allows its subjects to carry contraband goods to a belligerent. The risk of seizure and confiscation is deemed a sufficient penalty.