Municipal law is the national, domestic, or internal law of a sovereign state and is defined in opposition to international law. It encompasses the laws enacted by national, state, or local governments and is concerned with regulating the behavior of individuals, corporations, and entities within the country. Municipal law includes various branches such as criminal law, private law, administrative law, and constitutional law. It is enforced by domestic courts and administrative bodies.

Municipal law is tailored to the unique needs, values, and circumstances of the specific political entity it governs. For instance, traffic regulations, criminal codes, and property laws are all examples of municipal laws that vary from one country to another.

• Scope and jurisdiction: Municipal law applies within a specific country, while international law applies to relations between states and international entities.
• Sources of law: Municipal law is derived from a country's constitution, statutes, regulations, and case law. International law is based on treaties, international agreements, and customary international law.
• Enforcement: Municipal law is enforced by domestic legal and administrative institutions. International law relies on international bodies, diplomatic efforts, and mutual consent for enforcement.
• Focus: Municipal law addresses internal matters of a state, including criminal justice, civil disputes, and regulatory issues. International law deals with issues such as diplomatic relations, trade agreements, and global security.

Article 27 of the Vienna Convention on the Law of Treaties from 1969 provides that if a treaty conflicts with a state's municipal law (including the state's constitution), the state is still obliged to meet its obligations under the treaty. The only exception is provided by Article 46 of the Vienna Convention if a state's expression of consent to be bound by a treaty was a manifest violation of a "rule of its internal law of fundamental importance".^[1]

• Reydams, Luc Universal Jurisdiction: International and Municipal Legal Perspectives, (Oxford Monographs in International Law), (Oxford University Press, 2004) ISBN 978-0-19-927426-0.
• Paolo Davide Farah e Piercarlo Rossi, "National Energy Policies and Energy Security in the Context of Climate Change and Global Environmental Risks: A Theoretical Framework for Reconciling Domestic and International Law Through a Multiscalar and Multilevel Approach", European Energy and Environmental Law Review (EEELR), Kluwer Law International, Vol. 20, No. 6, pp. 232–244, 2011.