The ICJ’s opinion is not entirely clear. What is clear is that the use of nuclear weapons other than for self-defence is always unlawful. However, under treaty and customary law it is not unlawful to possess nuclear weapons. The Court noted that nuclear weapons are incapable of discriminating between military and civilian objectives and, as such, are contrary to the laws of war. Nonetheless, in urgent situations where the very existence of a nation is under threat from a nuclear attack, the use of similar weapons as a means of self-defence may not be unlawful. The opinion has been criticized because it approached its subject matter from a very legalistic viewpoint.

Nicaragua claimed that the USA had financed and supplied arms to a rebel group, the contras, in order to launch attacks against its legitimate government. It also claimed that US agents had trained the contras. The USA argued that it was merely acting in collective self-defence in favour of Nicaragua’s three neighbouring States, which Nicaragua had attacked. The basic question before the Court, for the purposes of this chapter, was whether this level of assistance amounted to an armed attack.

The Court’s assessment as to the criteria for an armed attack was provided earlier in the chapter (‘The meaning of armed attack’). In relation to the specific circumstances of this case, the ICJ held that the mere delivery of assistance to rebels in the form of weapons or logistical support does not amount to an armed attack. This was in line with the Court’s requirement of gravity, which is essential for an attack to be classified as an armed attack. This gravity test seems to have been slightly watered down in the Oil Platforms case.