Sometimes when the state and federal governments have concurrent authority, the federal government can decide to regulate that area exclusively. In such a situation, the state law is unconstitutional according to the doctrine of federal subrogation.

The correct answer would be the doctrine of federal preemption.

Explanation:

Clause II of Article VI of the U. S. Constitution states that federal law is the "supreme law of the land." It implies that every judge of state and other courts must follow the federal laws of the Constitution.

This clause, often termed as Supremacy Clause, allow federal laws to preempt state laws, even when both the state and federal governments have concurrent authority over a particular subject.

The doctrine of federal preemption simply implies that higher court may arrogate the law of a lower court if the two authorities come into conflict.