Les juges constitutionnels

Custom

1. Distinction between "custom" and "usage"; "custom" and "habit"

* Custom vs. Usage: "Custom" refers to an established practice that is accepted and considered legally binding, particularly in international law. "Usage" refers to a mere repeated practice, but without legal obligation. Every "custom" includes a "usage," but not every "usage" becomes a "custom."

custom = a general practice accepted as law and has binding force in inter law

usage = habitual practice of states that are not legally binding. These practises are followed out of courtisy, convenience/tradtion, not by a legal obligation

* Custom vs. Habit: A "habit" is an individual or collective repeated behavior, but it lacks the social or legal recognition of being obligatory. A "custom" implies normative acceptance within a community or legal system, whereas a "habit" is just a routine.

Habit = repeated behavior but in itself it lacks the normative demension required for it to become law. For a habit to become customory in inte law, it must be accompagnied by opinio juris.

The difference between all this terms is opinio juris, legal obligation

2. State Practice in Customary International Law

a. What constitutes state practice?

* State practice can include actions but also omissions, provided they reflect a legal intention.

* A vote in the UN General Assembly can be an indication of state practice, but its weight depends on the context. Since General Assembly resolutions are non-binding, they serve more as an indicator rather than definitive proof of customary law. However, Security Council resolutions, which are binding, may carry more weight.

* Statements by executive, legislative, or judicial bodies can constitute evidence of state practice, depending on their nature and context. It is relevant which internal organ acts, as some have more authority over international relations than others.

b. Can omissions be state practice?

* Omission can qualify as state practice if it is deliberate and reflects a legal conviction (e.g., refraining from claiming sovereignty over a territory).

* The absence of action must be analyzed within its context to determine whether it signals a legal norm.

c. How general must state practice be?

* State practice must be sufficiently widespread to establish a custom, but there is no precise number of states required.

* The practice of states most affected by the rule is particularly relevant. Some states' practices may carry more weight (e.g., major powers).

* Can a powerful state like the United States block a customary rule if the majority disagrees? In theory, no; in practice, opposition from an influential state can delay or complicate the rule's recognition.

* Regional customary international law (e.g., inter-American law) and even bilateral customary law (if two states consistently engage in a practice they recognize as binding) can exist.

d. How consistent must state practice be?

* State practice must be reasonably consistent, but minor inconsistencies do not necessarily invalidate a customary rule.

* The time required to form a custom varies. Traditionally, long periods were required, but today, customs can emerge quickly if the practice is widespread and accepted as law (e.g., the prohibition of chemical weapons).

* Instant customary law is possible when there is immediate consensus on a norm of fundamental importance (e.g., humanitarian law following a war crime). Is this desirable? Yes, in cases of moral or security necessity, but it may raise issues of legitimacy and legal clarity.

3. The Role of Opinio Juris in Customary International Law

a. Definition and necessity of opinio juris

* Opinio juris sive necessitatis means that states follow a practice because they believe it is legally obligatory, not just out of habit.

* Repeated practice alone is insufficient—there must be a belief in the rule’s legal necessity.

b. How is opinio juris determined?

* Consistency of state practice is an indicator but is not enough on its own; opinio juris must be demonstrated separately.

* It is not merely a tacit agreement among states—habit alone does not create law.

* Some argue that customary law consists of both state practice and opinio juris, while others believe that over time, widespread practice naturally implies opinio juris.

c. Can opinio juris be assumed?

* A rule does not become customary just because it is socially necessary—there must be normative acceptance by states.

* If all states agree on a rule in principle but none act accordingly, it cannot become a customary norm.

d. Who determines opinio juris?

* Can states have opinions? In international law, we refer to the positions of governments and their diplomats.

* But who speaks for the state? The head of state, parliament, judiciary? This depends on the context and the state’s legal system.

* If a government is not representative, does its opinion count? In international law, official authority matters, not democratic legitimacy.

4. Who is bound by customary international law?

* Are dissenting and non-participating states bound? Yes, unless they have consistently and explicitly objected from the beginning.

* Persistent objector rule: A state must clearly and repeatedly express its opposition before the rule becomes customary.

* Late objections (after the custom is established) are generally ineffective unless they contribute to an evolving legal standard.

* Are new states bound by pre-existing customary law? Generally, yes, unless they object to a developing custom from the

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