Who can declare a bill to be unconstitutional?

The Supreme Court is the definitive authority on determining the constitutionality of laws in the United States. This power is derived from the principle of judicial review, which was established in the landmark case Marbury v. Madison in 1803. Through judicial review, the Supreme Court can evaluate laws passed by Congress and actions taken by the executive branch to ensure they align with the Constitution. If a law is found to contradict constitutional principles, the Court has the authority to declare it unconstitutional, effectively rendering it void and unenforceable.

In contrast, Congress can pass legislation but does not possess the power to unilaterally declare a law unconstitutional. The President's role includes enforcing laws but does not extend to adjudicating their constitutionality. Similarly, while the Attorney General may provide legal opinions and represent the government in legal matters, the authority to declare a bill unconstitutional rests solely with the judiciary, specifically the Supreme Court. This system of checks and balances ensures that no single branch of government has unchecked power, maintaining the integrity of the Constitution.