Customary International Law

Question 1

Customary International Law

Answer 1

General and consistent practice of states followed from a sense of legal obligation
Ex: state practice (diplomacy) and opinio juris

Question 2

Opinio juris

Answer 2

Belief or practice rendered obligatory by rule of law. May be inferred from acts or omissions

Question 3

Elements of Customary Law

Answer 3

• General and consistent practice (but which needn’t be universal)
• Specially Affected States: if important actors don’t consent to practice, it can’t mature into rule of customary law
• Persistent Objectors: must do so early and consistently. Doesn’t apply to states not around at the time rule comes into being

Question 4

Jus Cogens Norms

Answer 4

A treaty is void if, at time of conclusion, it conflicts with norm of general international law
Ex: prohibition on unlawful use of force, slavery, apartheid

Question 5

How customary law changes

Answer 5

• Large numbers of states agree
  -Conduct consistent with new rule
  -Indications of opinio juris toward new rule

Question 6

Treaty v. Customary Law

Answer 6

Treaties codify, crystallize, and create new norms, superseding existing custom

Custom: exists without treaty, and alongside consistent treaties/ fills gaps left by treaties