Written and Unwritten International Law

Overview

• Lecture discusses types of international law: written and unwritten.
• Emphasizes distinction between treaties (written) and customary law (unwritten).
• Explains how customs become legally binding and may later be codified.

Written International Law

• Written laws are usually treaties, conventions, or protocols.
• Examples: Geneva Convention, Kyoto Protocol.
• Treaties function like contracts countries sign and ratify.
• Written laws are explicit and recorded in formal documents.

Customary (Unwritten) International Law

• Unwritten rules between states are called customs or norms.
• Legal term for these is customary law.
• Customs reflect widespread state practice and a sense of legal obligation.
• Example norm: prohibition on invading another country.
• All states must follow customary law, even without explicit agreement.

Relationship Between Customary Law and Treaties

• Many customary rules eventually become written down.
• UN Charter contains examples of customs that were later codified.
• Codification converts widely accepted norms into formal treaties.

Key Terms and Definitions

• Treaty: A written international agreement between states, like a contract.
• Convention/Protocol: Specific types of treaties with particular scopes.
• Customary Law: Unwritten norms resulting from consistent state practice and legal belief (opinio juris).
• Norm: A general standard of behavior expected of states.

Action Items / Next Steps

• Review major treaties (e.g., Geneva Convention, Kyoto Protocol) for concrete examples.
• Study how customary law is identified: state practice + opinio juris.
• Examine the UN Charter to see codified customary norms.