International law and municipal law

International Law · Nature and sources. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

Two theories explain how international law relates to national (municipal) law. Monism sees one single legal order, in which international law can be applied by national courts directly. Dualism sees two separate systems: international law binds states among themselves, and it reaches national courts only when national law brings it in.

In practice, under incorporation a rule is part of national law automatically; under transformation it must first be made national law by a statute. Britain and Pakistan follow the dualist approach to treaties: the executive makes a treaty, but an Act of the legislature is needed before it changes rights inside the country.

Rules to remember

Monism: one legal order (Hans Kelsen). Dualism: two separate orders (Triepel, Anzilotti).
Incorporation: customary international law is part of the law of the land without legislation (Blackstone), unless it conflicts with an Act of Parliament.
Transformation: a rule applies in national courts only after a statute or other domestic act adopts it.
Self-executing treaty provision: courts can apply it directly; non-self-executing: it needs implementing legislation.
US Constitution, Article VI: treaties are part of the supreme law of the land.
French Constitution 1958, Article 55: ratified treaties rank above statutes, subject to reciprocity.
Vienna Convention on the Law of Treaties 1969, Article 27: a state may not use its internal law as an excuse for not performing a treaty.

Common mistake

Students think that an unimplemented treaty does not bind a dualist state at all. It has no force in the national courts, but the state is still bound on the international plane and is responsible if it fails to perform.

Worked example

A dualist state ratifies a treaty giving foreign investors a right to tax relief. Parliament passes no law. An investor claims the relief in the national tax court, relying only on the treaty. What happens?

In a dualist system a treaty made by the executive is not part of national law until legislation transforms it.
No statute has been passed, so the court has no domestic rule to apply and the claim based on the treaty alone fails.
On the international plane the state is still bound, and it cannot plead its own law to excuse non-performance (Article 27, Vienna Convention 1969).

Answer: The court refuses the claim, but the state remains internationally responsible to the other treaty party.

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