The International Court of Justice's decision in the Nicaragua case of 1986 revolved around the actions of the United States concerning the Contras' rebellion in Nicaragua. The court's rulings can be analyzed as follows:
1. Justification of Self-Defense: The ICJ rejected the justification of self-defense presented by the United States, indicating that the conditions for claiming self-defense under international law were not met. This ruling aligns with option II.
2. Violation of Customary International Law: The ICJ concluded that the intervention of the United States in supporting the Contras' rebellion was indeed violative of customary international law, confirming that such actions were not legally justified under the norms governing international relations. This conclusion supports option III.
Combining these findings, the correct choice is II and III, as they accurately reflect the court's ruling regarding the United States' actions in the case.