International Law and Domestic Legal Systems Integration

International Order and State Legal Systems

The creation of legal norms occurs at two levels: domestic and international. There is an inevitable relationship between these systems, which gives rise to two primary challenges: the integration of international standards into domestic relations and the hierarchy of standards once international law becomes part of domestic law.

General Scheme of Relations

The basic rule is the supremacy of international norms. In the event of a conflict, international standards prevail, leading to two key consequences:

• States are obliged to modify their domestic law to comply with international standards.
• A state may not plead its internal laws, or even its constitution, to avoid complying with international obligations.

Reception of International Norms

Customary Norms

Customary norms are incorporated into domestic law without formal ceremonies. They become part of state law automatically based on the following principles:

• Integration occurs automatically without express acts by authorities.
• It has a general nature affecting all international customs binding upon Spain.
• It applies only to customs that specifically require Spanish compliance.
• The custom becomes part of Spanish law the moment it crystallizes through practice and opinio iuris.

Conventional Rules

The reception of conventional standards (treaties) is of significant interest as domestic judges apply them more frequently than customary law. This process is never automatic and requires an explicit act, such as the adoption of national legislation or the official publication of the treaty.

Internal Acts of International Organizations

Resolutions from international organizations are mandatory for Spain, though their reception is not explicitly governed by Spanish law. Practical implementation is achieved through internal rules, such as Ministerial Ordinances. For example, UN Security Council resolutions regarding economic sanctions are implemented via ministerial decrees to regulate economic relationships with specific states.