Am 21. Dezember 1965 verabschiedete die UN Vollversammlung ohne Gegenstimmen die Resolution 2131 (XX) als Präzisierung der UN Charta. Unter dem Titel Declaration on the Inadmissibility of Intervention in the Domestic Affairs of States and the Protection of Their Independence and Sovereignty steht dort:
2. No State may use or encourage the use of economic, political or any other type of measures to coerce another State in order to obtain from it the subordination of the exercise of its sovereign rights or to secure from it advantages of any kind.
(...)
In the mid-1980s, the International Court of Justice, seized of the issue by the Nicaraguan Government which had complained of active military, logistical and other support by the United States to Contras rebel groups within Nicaraguan territories and to other actions including the United States’ mining of Nicaraguan ports and coastal waters, referred in its Judgement, inter alia, to resolution 2131 (XX) (Military and Paramilitary Activities in and Against Nicaragua, I.C.J. Reports, 1986, p. 107, para. 203).The new life of resolution 2131 (XX) as part of a general scientific and legal re-examination and restatement, in more contemporary terms than the old classical international law of the right to self-determination, political and economic, free from unilateral interventions or threats thereof by other States or groups of States was perhaps demonstrated in the political aftermath to the NATO armed intervention against the former Yugoslavia in early 1999, without any prior enabling legal resolution from the Security Council.
https://legal.un.org/avl/ha/ga_2131-xx/ga_2131-xx.html
Diese Resolution ist damit auch vom IGH bereits mehrfach in Urteilsbegründungen herangezogen worden.