Prof. Casis delivers annual Edgardo J. Angara Professorial Chair Lecture

Professor Rommel J. Casis examined customary international law in his Edgardo Angara Professorial Chair Lecture at Bocobo Hall on 24 October 2019.

In his lecture, “Re-Customizing Customary International Law,” Professor Casis discussed specifically one source of international law namely the Statute of the International Court of Justice. He argued that although custom is the lifeblood of international law, the concept is still problematic in many ways. His critique on customary international law as it now stands, restedmainly on the two elements of custom in general: state practice, and opinio juris (belief that a rule exists as law). According to Professor Casis, there is difficulty in applying or even understanding these elements since distinguishing practice from opinion is often a troubling task; historically, these have not been applied in analyzing whether or not a custom exists.

As a way forward, Prof. Casis proposed a “re-customization” of the concept of customary international law. Redefining opinio juris, giving weight to the elements on the basis of the international obligation itself, and making state practice evidence of opinio juris only, are among the solutions to be explored. In conclusion, Prof. Casis argued that the traditional approach of the ICJ, which is the strict application of the elements of custom, should be “tweaked” to conform to the international community as it exists today—a community with a greater number of states and more complex state relations.