b. International Custom

What is the definition of custom?

General and consistent practice of States followed by them from a sense of legal obligation. (Restatement (Third) of Foreign Relations Law of the United States)

What are the elements of International Custom?

• State practice. States must show consistent and uniform external conduct. Both their statements and their actions generally count as practice. Relevant considerations are the duration of the practice; its uniformity and consistency; and its generality, including the practice of States whose interests are specially affected (Bernas, Public International Law, 2009).
• Opinio juris sive necessitatis. In following a general practice, States must act from a sense of legal duty, rather than merely from courtesy, convenience, or tradition.

Acts must not only form a settled practice. Their character or manner of performance must also show a belief that a rule of law makes the practice obligatory (International Court of Justice, North Sea Continental Shelf Cases, cited in Mijares v. Ranada, G.R. No. 139325, April 12, 2005).

Unlike treaties, customary norms bind all States regardless of consent, subject to the persistent objector rule. The theory of tabula rasa does not extinguish obligations under customary international law.

No fixed period is required for a customary norm to form, provided that state practice and opinio juris are manifest (North Sea Continental Shelf Cases, ICJ, February 20, 1969).

The number of parties, express acceptance of legal rules, and, in some instances, the declaratory character of provisions can have a law-creating effect at least as strong as general practice sufficient to support a customary rule (Brownlie).

What is the element of state practice?

The practice must be consistent and general. However, consistency requires substantial uniformity and not necessarily complete uniformity in practice (Asylum Case (ICJ), November 20, 1950). Generality likewise does not require universality.

What is the evidence of state practice?

The following acts may evidence state practice:

• Diplomatic correspondence;
• Policy statements;
• Press releases;
• Opinions of official legal advisers;
• Official manuals on legal decisions (executive decisions and practices, and government comments on drafts by the ILC);
• International and national judicial decisions;
• Recitals in treaties and international instruments;
• Practice of international organs (HARRIS)

UN General Assembly resolutions are generally just recommendations. However, such resolutions may be an evidence of state practice that is relevant in the development of custom. (See Nicaragua Case (ICJ, June 27, 1986).

What is the element of opinio juris give necessitates (opinion of law or necessity)?

What is the element of opinio juris sive necessitatis (opinion of law or necessity)?

This refers to the belief on the part of states that a particular practice is required by law, and not because of courtesy or political expedience (North Sea Continental Shelf Cases (ICJ) February 20, 1969).

It is the existence of opinio juris that distinguishes binding custom from mere usage, from comity, and from courtesy or protocol.

Custom may be:

• General, which is binding upon all or most states; or
• Particular, which is binding only between two or among a few states.

The ICJ has recognized the possibility of regional custom (Asylum Case (ICJ) November 20, 1950) and of bilateral custom (Right of Passage over Indian Territory Case (ICJ) April 12, 1960).

What is regional custom?

A practice among states within a particular area of the world which can be sufficiently well established and accepted as law that is binding among the states of that region but not elsewhere.

What is instant custom (Diritto Spontaneo)?

Customary law may emerge even within a relatively short period of time, if within that period, State practice has been uniform and extensive. It comes out as a spontaneous activity of a great number of states supporting a specific line of action. (Bernas, Public International Law, 2009).

What is special or local custom?

A long continued practice between two states, accepted by them as regulating their relations that form the basis of mutual rights and obligations. (Portugal v. India (ICJ), April 12, 1960).

Rules in case of conflict between a treaty and a custom

• If the treaty comes after a particular custom- treaty prevails, as between the parties to the treaty.
• If a customary rule develops after a treaty, it does not automatically prevail over the treaty between its parties. Determine whether the treaty has been modified or terminated under the applicable law of treaties; a conflicting peremptory norm is a separate exception.