Step 1: Understanding the Concept:
The question asks to which area of international law the "constitutive" and "declaratory" theories belong. These are two fundamental and opposing theories that explain the legal effect of recognizing a new state.
Step 2: Detailed Explanation:
The two main theories of State Recognition are:
1. Constitutive Theory: According to this theory, an entity does not become a state under international law until it is recognized as such by other existing states. The act of recognition "constitutes" or creates the statehood. It is a necessary precondition.
2. Declaratory Theory: This theory holds that an entity becomes a state as soon as it meets the factual criteria for statehood (defined territory, permanent population, government, and capacity to enter into relations with other states), as laid down in the Montevideo Convention. The act of recognition by other states is merely a formal acknowledgment or "declaration" of an already existing fact. It does not create the state.
These theories are central to the debate on how and when a new state legally comes into existence.
Step 3: Final Answer:
The constitutive and declaratory theories relate to State Recognition.