In the U.S., the responsibility for interpreting the constitutionality of laws lies primarily with the Supreme Court. This court has the ultimate authority to review legislation and executive actions to ensure compliance with the Constitution. Through the process of judicial review, the Supreme Court can declare laws unconstitutional, thereby nullifying them. This important function serves as a check on legislative and executive power, maintaining the balance between branches of government. The Court's interpretations can have far-reaching implications on civil rights, liberties, and the overall functioning of democracy in the United States.