Which branch of government has the authority to declare laws unconstitutional?

The judicial branch has the authority to declare laws unconstitutional as it serves as the guardian of the Constitution. This power is primarily exercised through judicial review, a concept established by the landmark Supreme Court case Marbury v. Madison in 1803. Judicial review allows courts to evaluate the constitutionality of legislative acts and executive actions. When the judicial branch determines that a law conflicts with the Constitution, it has the responsibility to strike it down, ensuring that no legislation or executive order can supersede the fundamental principles outlined in the Constitution. This mechanism is crucial for maintaining the rule of law and protecting individual rights, reinforcing the principle of checks and balances among the branches of government.

The legislative branch is responsible for making laws, while the executive branch enforces them, so they do not have the authority to nullify legislation. The state governments also do not have the power to declare federal laws unconstitutional, as this authority is reserved for federal courts.