Relationship between international law and municipal law

1. Dualism

Associated with Triepel (1899) and Anzilotti. International law and municipal law are two separate systems.

• Different subjects: international law regulates States; municipal law regulates individuals.
• Different sources: the common will of States, against the will of a single State.
• Different substance: relations between sovereigns, against relations within a State.

Consequence: a rule of international law cannot operate inside a State until it has been transformed into municipal law by an act of the State. If the two conflict, a municipal court applies municipal law.

Criticism: international law today does regulate individuals (war crimes, human rights, piracy); and the State's will is itself limited by international law, so the two are not wholly separate.

2. Monism

Both are parts of a single legal order. Kelsen, applying his pure theory, traced all law to a single basic norm and treated international law as superior, since it fixes the limits of each State's jurisdiction. Lauterpacht argued from the other side: the individual is the ultimate unit of all law, and international law is supreme because it protects human beings. Some writers (an extreme minority) gave primacy to municipal law, which amounts to denying international law altogether.

Criticism: in practice national courts do give effect to statutes that conflict with international law, and a monist account cannot explain that.

3. Coordination (harmonisation) theory

Fitzmaurice and Rousseau: the two systems do not come into conflict as systems because they operate in different fields. Each is supreme in its own sphere. What can conflict is an obligation: if a State's law prevents it from doing what international law requires, the municipal law remains valid internally, but the State is responsible internationally. This matches Article 27 of the VCLT, which provides that a party may not invoke its internal law as justification for failure to perform a treaty, and Article 3 of the 2001 Articles on State Responsibility.

4. Transformation and incorporation

• Transformation: a rule binds internally only after it has been adopted by statute or other legislative act (dualist).
• Incorporation (adoption): international law is automatically part of the law of the land (monist), unless excluded by statute.

United Kingdom. Custom is incorporated: Blackstone said the law of nations is held to be part of the law of the land. R v. Keyn (The Franconia, 1876) appeared to require transformation, and Parliament responded with the Territorial Waters Jurisdiction Act, 1878. Chung Chi Cheung v. The King (Privy Council, 1939) restated incorporation, subject to statute and binding precedent. Trendtex Trading Corporation v. Central Bank of Nigeria (Court of Appeal, 1977) confirmed that custom is incorporated as it changes. But a statute prevails over custom: Mortensen v. Peters (Scotland, 1906). Treaties are different: they require an Act of Parliament to have domestic effect, because treaty-making is an executive act and the Crown cannot change the law without Parliament.

United States. Custom is part of US law: “International law is part of our law” (The Paquete Habana, US Supreme Court, 1900). By Article VI of the US Constitution, treaties are part of the supreme law of the land. A self-executing treaty applies directly; a non-self-executing one needs legislation (Foster v. Neilson, 1829; Medellín v. Texas, 2008).

5. India

The constitutional provisions.

• Article 51(c) (Directive Principle): the State shall endeavour to foster respect for international law and treaty obligations in the dealings of organised peoples with one another.
• Article 73: the executive power of the Union extends to matters on which Parliament can legislate, which includes Entry 14 of List I (entering into treaties and agreements with foreign countries and implementing them). Treaty-making is an executive act.
• Article 253: Parliament may make any law for the whole or any part of India for implementing any treaty, agreement or convention, or any decision of an international conference, notwithstanding the distribution of legislative powers.

The cases.

• Maganbhai Ishwarbhai Patel v. Union of India, 1969 INSC 4, (1970) 3 SCC 400. The Rann of Kutch award of 1968 was challenged on the ground that implementing it would cede territory, which, under the Berubari opinion (1960 INSC 49), needs a constitutional amendment. The Court held that the award only determined an undefined boundary and did not cede Indian territory, so executive action was enough. It also explained that a treaty which does not affect the rights of citizens or alter the law can be implemented by the executive, but one that does needs legislation.
• Jolly George Varghese v. Bank of Cochin, 1980 INSC 19, (1980) 2 SCC 360. Article 11 of the International Covenant on Civil and Political Rights forbids imprisonment merely for inability to fulfil a contractual obligation. Krishna Iyer J. held that the Covenant, until incorporated, does not by itself override a domestic statute (section 51 of the Code of Civil Procedure), but read section 51 in the light of Article 21 and the Covenant so that a debtor may be detained only where there is some element of bad faith or wilful refusal despite means to pay. This is the dualist statement with a harmonising method.
• Gramophone Company of India Ltd. v. Birendra Bahadur Pandey, 1984 INSC 40, (1984) 2 SCC 534. Records in transit through India to Nepal. The Court held that the comity of nations requires rules of international law to be accommodated in municipal law even without express legislative sanction, provided they do not run into conflict with Acts of Parliament. Where they conflict, the statute prevails. Treaties must be made part of municipal law by legislation, but national courts will try to construe statutes in harmony with them.
• Vishaka v. State of Rajasthan, 1997 INSC 604, (1997) 6 SCC 241. There was no Indian law on sexual harassment at the workplace. The Court used the Convention on the Elimination of All Forms of Discrimination against Women (CEDAW), which India had ratified, to read content into Articles 14, 15, 19(1)(g) and 21, and laid down guidelines to operate until Parliament legislated. Any international convention not inconsistent with fundamental rights and in harmony with their spirit must be read into them. Parliament later enacted the Sexual Harassment of Women at Workplace (Prevention, Prohibition and Redressal) Act, 2013.
• Vellore Citizens Welfare Forum v. Union of India, 1996 INSC 952, (1996) 5 SCC 647. The precautionary principle and the polluter-pays principle were held to be part of customary international law and therefore part of the law of the land, there being no conflict with domestic law.

6. The international side of the relationship

Before an international tribunal, municipal law is treated as a fact, and a State cannot rely on its own law to escape an international obligation: Alabama Claims arbitration (USA v. UK, 1872), where Britain's lack of a law to stop the building of Confederate warships was no defence; the PCIJ's opinion on the Treatment of Polish Nationals in Danzig (1932); and Article 27 of the VCLT. The exception is Article 46 VCLT, which lets a State invalidate its consent only if it was given in manifest violation of an internal rule of fundamental importance on competence to conclude treaties.

How this is examined

The essay “Explain the theories relating to the relationship between international law and municipal law” was set in February 2025 and August 2024; “Monism” was a short note in June 2025. For the essay, give dualism and monism with criticism, the coordination theory, then the practice of the UK, the US and India. The Indian section should name Articles 51(c), 73 and 253 and at least Gramophone, Jolly George Varghese and Vishaka. For a short note on monism, state Kelsen's and Lauterpacht's versions, the criticism and one sentence on how India departs from it for treaties.