Which body is primarily responsible for interpreting if a law is unconstitutional?

The Supreme Court is the body primarily responsible for interpreting whether a law is unconstitutional. This power is derived from the principle of judicial review, established in the landmark case Marbury v. Madison in 1803. Judicial review allows the Supreme Court to examine laws and actions by the legislative and executive branches to ensure they comply with the Constitution.

The Supreme Court's role is critical because it acts as a check on legislative and executive powers, ensuring that any laws passed or actions taken do not violate constitutional principles. This interpretation is essential for upholding the rule of law and protecting individual rights.

Other bodies, like Congress or the President, do not have the authority to declare laws unconstitutional. While Congress is responsible for passing legislation and the President enforces laws, neither has the power to interpret the Constitution formally in a judicial sense. State legislatures may create laws pertinent to their jurisdictions, but any law they enact can still be reviewed by the Supreme Court for constitutional compliance.