Public International Law, in its traditional sense, is the branch of public law that regulates the relations of states and other entities that have been granted international personality. Its modern definition, however, is that it is a branch of law that deals with the conduct of states and international organizations, their relations with each other, and, in certain circumstances, their relations with persons, whether natural or juridical.[1]
Public International Law should be distinguished from Private International Law. The latter pertains to the branch of domestic law dealing with disputes that arise from private transactions between individuals or companies and corporation from one country vis-à-vis their counterpart.[2] It determines whether or not our Philippine courts should assume jurisdiction of a particular cross-boarder issues, and whether Philippine laws or that of another country’s legal system is applicable in a particular case.
Article 38 of the Statute of International Court of Justice enumerates the primary and secondary sources of public international law. Its primary sources are; (1) International Conventions, whether general or particular, establishing rules expressly recognized by the contesting states, or simply referred to as “Treaties”; (2) International Custom, as evidence of a general practice accepted as law; (c) The general principles of law recognized by civilized nations. Article 38 (d) provided that subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.
International Conventions or Treaties. Under Article 2 of Vienna Convention on the Law of Treaties, Treaty means an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation.
Under our present constitution, it is the President who is vested with the power to ratify treaties, subject to the concurrence of the Senate. The role of the Senate is limited only to giving or withholding its consent, or concurrence to the ratification. It is within the authority of the President to refuse to submit a treaty to the Senate, or, having secured its consent for ratification, refuse to ratify it. There is no legal obligation to ratify a treaty, but it goes without saying that the refusal must be based on substantial grounds and not on superficial or whimsical reasons.[3]
International Custom or Customary International Law. It is consist of acts which, by repetition of similar international acts by states over number of years, occur out of a sense of obligation and are taken up by a significant number of states. It is based on custom, which is a clear and continuous habit of doing certain actions, which has developed under the conviction that such actions are, according to international law, obligatory or a matter of right. Thus, customary international law requires the concurrence of two elements; [1] The established, wide-spread, and consistent practice on the part of the States; and [2] A psychological element known as opinio juris sive necessitatis (opinion as to law or necessity). Implicit in the latter element is the belief that the practice in question is rendered obligatory by the existence of a rule of law requiring it.[4]
General Principles of Law. Some legal scholars and judges look upon certain “general principles of law” as a primary source of international law because they possess the “character of jus rationale” and are “valid through all kinds of human societies.” O’Connell holds that certain principles are part of international law because they are “basic to legal systems generally” and hence part of the jus gentium. These principles, he believes, are established through a process of reasoning based on the common identity of all legal systems. If there should be doubt or disagreement, one must look to state practice to determine whether the municipal law principle provides a just and acceptable solution.[5]
Where, in certain cases, there is no applicable treaty nor a generality of state practice giving rise to customary law, the international court is expected to rely upon certain legal notions of justice and equity in order to deduce a new rule for application to a novel situation.[6]
[1] Introduction to Public International Law 2022, Antonio E.B. Nachura
[2] Idem
[3] G.R. No. 158088, July 06, 2005
[4] G.R. No. 238875, March 16, 2021
[5] Idem
[6] Idem