1. Monism: This theory posits that international law and municipal law are part of a single, unified legal system. International law is considered superior and directly applicable within the domestic legal order. Municipal law must conform to international law, and if there's a conflict, international law prevails. This is often seen in civil law systems.
2. Dualism: This is the more prevalent theory, especially in common law systems. It views international law and municipal law as distinct and separate legal systems with different sources, subjects, and enforcement mechanisms. International law only becomes part of municipal law after it's specifically incorporated or transformed into domestic legislation through a formal process (e.g., ratification of a treaty followed by domestic legislation implementing it). If there's a conflict, the municipal law prevails unless the domestic law specifically allows international law to override it.
3. Harmonization: This approach seeks to find a balance between monism and dualism. It acknowledges the distinct nature of the two systems but emphasizes the importance of cooperation and coherence between them. States strive to align their domestic laws with international obligations, promoting compatibility and minimizing conflicts.
Practical Application and Nuances:
* Treaty Implementation: Many international treaties require states to incorporate their provisions into their domestic law through legislation or other means. This is a clear example of the dualist approach, demonstrating how international law needs domestic action to have effect within a state.
* Customary International Law: The application of customary international law (rules accepted by states as binding despite the absence of a written treaty) is more complex. Some argue it's directly applicable in municipal courts (monist view), while others require incorporation or demonstration of its acceptance into domestic jurisprudence.
* Judicial Interpretation: Courts often play a crucial role in determining the relationship between the two systems. Their interpretations can reflect a monist or dualist leaning, influencing how international law impacts domestic legal proceedings.
* International Courts and Tribunals: Decisions of international courts and tribunals have limited direct effect on municipal law unless a state voluntarily accepts their jurisdiction and agrees to implement the judgment. However, these decisions can influence domestic legal developments and shape judicial interpretations.
* Supranational Organizations: The European Union is a prime example of a supranational entity where international law (EU law) directly overrides municipal law in member states. This represents a significant departure from traditional dualist views.
In reality, the relationship between international and municipal law is often a nuanced mixture of monist and dualist elements, varying considerably depending on the specific legal issue, the state involved, and the specific legal system in question. The trend seems to be toward greater harmonization and a recognition of the growing interdependence between international and domestic legal orders.