Most international treaties order the relations between two States only. They create mutual rights and obligations and coordinate State behavior on a bilateral basis. While allowing for flexible solutions depending on the specific situation and interests of the States involved, bilateralism also inhibits the emergence of an international community that is ordered on the basis of general and uniform principles. Bilateralism puts the State, its sovereignty, and its consent to the creation of international law center stage and secures the precedence of State interests over interests outside or beyond its realm. This fortification of the State coined the traditional understanding of international law as it developed throughout the nineteenth and most of the twentieth century. It characterized its doctrine of sources by strictly focusing on State consent, it denied international law subjectivity to non-State actors, and de facto coupled the enforcement of international law to a favorable distribution of power in a non-hierarchical order. Within this framework, the international treaty was essentially a “workhorse of bilateralist international law” that coordinated State behavior by entering into quid pro quo bargains based on the underlying power relations and national interests.

Multilateralism, by contrast, assumes the existence and legitimacy of interests of an international community beyond the interests of States. It does not order inter-State relations on the basis of bilateral bargains, but rather on the basis of general principles that establish a general framework for the interactions among States and their citizens. It aspires toward universal validity and application and views States as being embedded within the structure of an international community.