The Supreme Court serves what important function in the U. S. federal
government?

It determines whether any actions by the executive and legislative branches are unconstitutional.

Explanation:

Article III of the U.S. Constitution gives the judicial branch the power to interpret laws and it is vested in the SC of the U.S.A. and it is applied to all the inferior courts. Judicial Review was established as a prominent doctrine of U.S.A. SC in 1803, Marbury versus Madison judgement which gave powers to the judiciary or SC to determine the Constitutionality of any executive or legislative laws.

The U.S.A. Constitution works on the principle of “separation of powers” which gives the powers to the judiciary to have “checks and balances” in the system. The rationale behind checks and balances is that neither of the branches can become too much powerful. Judicial Review is the most important tool of the judicial system of any country.The key founder of this concept of the judiciary was the United States and it is fundamental to them.

Judicial Review gives powers to U.S. Supreme Court to invalidateany law which violates the Constitution. Supreme Court can have a check on all the branches of government, whether it is Congress or State Government of any state.

The Judicial review has been taken from Article III and Article VI of the U.S. Constitution.

The historic judgement which is the landmark in the judicial review concept is Marbury versus Madison case of 1803 given by Supreme Court’s Judge John Marshall.

The Court has declared the law made by Congress as unconstitutional and said that the only judiciary must have to determine that what law states, and whether that law abides by the constitution.

If there is the conflict between the laws of government and the laws in the constitution, then it is the power of the Supreme Court to decide which law will prevail.