Marbury v. Madison The 1803 Marbury v. Madison case resulted in the most important Supreme Court decision in history. The court's ruling established the power of judicial review, solidified the Constitutional system of checks and balances, strengthened the power of the federal government, and made the Judiciary an equal partner with the Legislative and Executive branches of government. In the Election of 1800, Thomas Jefferson and his anti-federalist Republican party defeated the incumbent John Adams and the Federalist party. The Republicans also won a majority in Congress. In an effort to keep at least one branch of the government under Federalis