By Otto Spijkers

In 1970, Thomas M. Franck wrote an article about changing norms governing the use of force, which he gave the following title: who killed Article 2(4)? It seems that the same Article 2(4) UN Charter is in trouble once again. On the same day (today), two interesting blog posts were published on the legal status of the prohibition to use force, as codified in Article 2(4). James Green questioned the peremptory status (jus cogens) of the prohibition of the use of force, and Natalie Oman argued that the use of force might be legal even without Security Council authorization.

Article 2(4) UN Charter prohibits the use of force by one State against another. Is this a norm which allows no derogation? Is it a supernorm? Is it jus cogens? Green argued that the norm of Article 2(4) UN Charter cannot be peremptory (jus cogens), inter alia because the Charter itself already allows two exceptions: self-defense and UN-authorized collective measures. It is thus derogable, and not jus cogens.  

This seems to be a minority view. After all, Article 2(4) UN Charter is one of the most popular examples of a peremptory norm
in view of the community of States. Judge Schwebel of the International Court of Justice pointed out that ‘[w]hile there [was] little agreement on the scope of jus cogens, it is important to recall that in the International Law Commission and at the Vienna Conference on the Law of Treaties there was general agreement that, if jus cogens has any agreed core, it is Article 2, paragraph 4 [of the UN Charter].’ See his Dissenting Opinion in the Case Concerning Military and Paramilitary Activities between Nicaragua and the United States of America (1984).

There are many problems with Article 2(4) UN Charter. It is still
unclear what the word ‘force’ means. The travaux preparatoires of the UN
Charter, and the many declarations adopted on the topic by the General Assembly, suggest that the use of force has to involve military measures, but it does not explicitly say anywhere in these documents that ‘force’ has to be military force. See the relevant paragraphs of General Assembly resolutions 42/22 (1987) and 2625(XXV, 1970). 

These and other problems can be avoided by arguing that the prohibition to use force is jus cogens, even though the formulation of this prohibition in Article 2(4) is not. But it is difficult to define the jus cogens-version of the prohibition to use force in such a way that it only partially corresponds with Article 2(4). Does the jus cogens-version of the prohibition to use force boil down to the prohibition to commit inter-State aggression? But what is the definition of aggression then? Is it the one adopted by the International Criminal Court? The Court has said nothing about any jus cogens. Etc. In any case, any jus cogens version of the prohibition to use force must also provide room for collective action and self-defense without seeing those as exceptions to the rule. After all, jus cogens norms allow for no exceptions; they are nonderogable. According to Green, (probably) no such norm has been
recognized as jus cogens by the community of States (he is a positivist, so he
does not want to base a jus cogens norm purely on morality and global values).

After having noticed all these problems, one might wonder what the added benefit is of labeling the prohibition to use force, or Article 2(4) UN Charter, as jus cogens. Do we really need it to be jus cogens? According to Natalie Oman, it does make a big difference.
If the Article 2(4) version of the prohibition to use force is not jus cogens, then States are allowed to use force against other States, if the aim is to defend jus cogens norms, such as the protection of individuals from war crimes, genocide, and crimes against humanity. In such case it is possible to ignore Article 2(4) and act legally anyways. But this is only possible when Article 2(4) is not jus cogens. If Article 2(4) is not jus cogens, then this would allow the international community to intervene in Libya at the moment, even without a Security Council authorization (as is required by the UN Charter regime, of which Article 2(4) UN Charter is an element). So it does indeed make a difference. Seeing what happens in Libya at the moment, one might be inclined to indeed kill Article 2(4) UN Charter, and claim that the duty to protect individuals from crimes against humanity etc. is of such importance that it overrides all other legal norms and obligations, including the prohibition to use force. This would make such a duty truly jus cogens (but it would create a lot of problems as well….).