Customary International Law vs. Domestic Law: A Comprehensive Analysis
Conflict Between Customary International Law and Domestic Law
As we have seen, the reception of customary international law into domestic law has been a major constraint. This constraint, for most countries, is rooted in the primacy of international law at the domestic level, even if its provisions are or seem contrary to domestic law. Only the German constitution explicitly establishes the principle of international law’s primacy over contrary domestic law.
Jurisprudence and legal scholars suggest that courts should strive to avoid internal conflict between international and domestic law by interpreting domestic law in a way that reconciles it with international law. This approach is based on the presumption that the legislature (Congress) did not intend to violate its international obligations. However, if the wording of the law is unclear and conflict persists despite attempts to harmonize the two standards, the judge must apply the law.
In this area, it is essential to remember that if a municipal court applies a domestic law that contradicts obligations under international law, the state judge effectively fulfills their duty as a national court but also commits an internationally wrongful act, which creates state responsibility.
Execution and Reception of Treaties
It is a common understanding that treaties containing provisions for adequate compliance by states parties should include measures for performance or reception at the domestic level of each state. For example, a treaty obligating contracting states to punish certain forms of air piracy or to confer specific franchises or customs on nationals of other contracting parties will not automatically apply domestically.
For a treaty to be implemented within each of the contracting states by the respective courts and administrative authorities, it requires execution or reception of its provisions. As with the reception of international customary law, international law does not impose a specific form or manner of execution on states. It only requires full compliance, allowing each state to take the domestic measures it deems necessary or useful to comply.
There are two common forms of execution to effect the reception of the treaty into the domestic order:
- A state can pass a law that reproduces the content of treaty obligations. Although this law was inspired by the treaty and issued in execution, it remains independent of the treaty’s fate.
- In countries where treaties must be approved by parliament or congress before ratification, the treaty may be introduced or brought into force in domestic law through a formality. For example, in France, the official publication of the treaty is performed. In Chile, the enactment and publication of the treaty occur. In the U.S., it is referred to as proclamation. This formality gives the treaty domestic value and force of law, requiring it to be applied as a law.
This last mode is useful only for treaties that are self-executing, meaning they contain adequate, complete, and detailed provisions that can be implemented by themselves. However, if the treaty is non-self-executing, or if some of its provisions are, legislation implementing the treaty will be needed. For example, if parties undertake to prevent and punish crimes committed against diplomatic agents and other internationally protected persons, the treaty will be executed internally through a law defining these offenses, establishing penalties, and extending the jurisdiction of national courts.
The issue of the status of the International Criminal Court is similar. Not only does it need to be ratified, but the state also undertakes, upon ratification, to adapt its domestic law in this area.