(1) Articles that are primarily and ordinarily used for military purposes in time of war, such as arms and munitions of war, military material, vessels of war, or instruments made for the immediate manufacture of munitions of war.
(2) Articles that may be and are used for purposes of war or peace, according to circumstances.
Articles of the first class, destined for ports of the enemy or places occupied by his forces, are always contraband of war.
Articles of the second class, when actually and especially destined for the military or naval forces of the enemy, are contraband of war.
In case of war, the articles that are conditionally and unconditionally contraband, when not specifically mentioned in treaties previously made and in force, will be duly announced in a public manner.
Art. 35. Vessels, whether neutral or otherwise, carrying contraband of war destined for the enemy, are liable to seizure and detention, unless treaty stipulations otherwise provide.
Art. 36. Until otherwise announced, the following articles are to be treated as contraband of war:
Absolutely contraband.—Ordnance; machine guns and their appliances and the parts thereof; armor plate and whatever pertains to the offensive and defensive armament of naval vessels; arms and instruments of iron, steel, brass, or copper, or of any other material, such arms and instruments being specially adapted for use in war by land or sea; torpedoes and their appurtenances; cases for mines, of whatever material; engineering and transport materials, such as gun carriages, caissons, cartridge boxes, campaigning forges, canteens, pontoons; ordnance stores; portable range finders; signal flags destined for naval use; ammunition and explosives of all kinds and their component parts; machinery for the manufacture of arms and munitions of war; saltpeter; military accouterments and equipments of all sorts; horses and mules.
Conditionally contraband.—Coal, when destined for a naval station, a port of call, or a ship or ships of the enemy; materials for the construction of railways or telegraphs; and money, when such materials or money are destined for the enemy's forces; provisions, when actually destined for the enemy's military or naval forces.