The national government's obligation to ensure water access is explicitly stated in the Constitution, which is the supreme law. When the government fails to enforce this constitutional obligation, it

The national government's obligation to ensure water access is explicitly stated in the Constitution, which is the supreme law. When the government fails to enforce this constitutional obligation, it is ignoring a direct legal mandate. This type of pressure, stemming from laws, regulations, and mandates, is known as coercive pressure in institutional theory.

a) Coercive pressure from the Constitution as the supreme law, which explicitly obliges the national government to ensure water access.

The final answer is $\text{a}$