Final answer:
The United States Supreme Court has the power to declare an act of Congress unconstitutional. This power is known as judicial review and acts as a check on the legislative branch.
Step-by-step explanation:
The United States Supreme Court has the power to declare an act of Congress unconstitutional. This power is known as judicial review, and it allows the Supreme Court to review laws and actions to determine whether they are in accordance with the Constitution.
For example, if Congress passes a law that is believed to be unconstitutional, the Supreme Court can hear a case challenging the law and ultimately declare it invalid. This power acts as a check on the legislative branch, ensuring that laws are in line with the principles of the Constitution.
In addition to declaring laws unconstitutional, the Supreme Court also hears cases involving federal law and serves as the nation's final court of appeal. This means that individuals or organizations can bring their cases to the Supreme Court after going through lower courts, with the Supreme Court having the power to make final decisions on these matters.