The major legal case that affirmed the principle of judicial review was Marbury v. Madison (1803). In this landmark decision, the Supreme Court, under Chief Justice John Marshall, ruled that the power of the judiciary includes the ability to determine the constitutionality of laws enacted by Congress. This case established the principle that the Supreme Court could strike down laws that it found to violate the Constitution, thus cementing the judiciary's role as a co-equal branch of government and reinforcing the idea of checks and balances within the American political system.