This is the power of a court to review a law or an official act of a government employee or agent for constitutionality or for the violation of basic principles of justice.

It is Judicial Review

The power of a court to review a law or an official act of a government employee for constitutionality is known as judicial review.

Explanation:

By means of judicial review the court decides whether a law or an official act of a government employee is in accordance with the US Constitution or violates or contradicts it. If the law or act is not in line with the Supreme Law, the law or act is directly declared unconstitutional and, therefore, null and void. The laws passed by Congress must observe the principles outlined in the US Constitution so as to be valid.

The Court established this doctrine in the case of Marbury v. Madison in 1803. It was the first time that the court declared a law unconstitutional.