Common Article 3 to the four Geneva Conventions encourages the parties to a non-international armed conflict to bring into force international humanitarian law provisions through the conclusion of special agreements. Since armed groups are ever more frequent participants in contemporary armed conflicts, the relevance of those agreements as means to enhance compliance with IHL has grown as well. The decision-making process of special agreements recognizes that all the parties to the conflict participate in the clarification and expansion of the applicable rights and obligations in a way that is consistent with the principle of equality of belligerents. This provides incentives for armed groups to respect the IHL rules they have themselves negotiated. However, even upon the conclusion of such agreements, it remains unclear which legal regime governs them. This paper will argue that special agreements are governed by international law instead of domestic law or a sui generis legal regime.

The equal application of international humanitarian law (jus in bello) to all parties to an international armed conflict is a cornerstone principle of jus in bello. In his article, Professor Mandel casts doubt on the legal basis of this principle. Reacting to this claim, this contribution demonstrates that the ‘equality of belligerents’ is a principle firmly grounded in both conventional and customary international law. Moreover, its legal force withstands the test of international jurisprudence, including the International Court of Justice's controversial Nuclear Weapons advisory opinion.