The court case that established judicial review is Marbury v. Madison. In 1801, outgoing President John Adams had issued William Marbury a commission as justice of the peace, but the new Secretary of State, James Madison, refused to deliver it. Marbury then sued to obtain it. With his decision in Marbury v. Madison, Chief Justice John Marshall established the principle of judicial review, an important addition to the system of “checks and balances” created to prevent any one branch of the Federal Government from becoming too powerful. The unanimous opinion was written by Chief Justice John Marshall, and it declared that acts of Congress that conflict with the Constitution are invalid and that the federal courts have the power to strike them down. The principle of judicial review has been a fundamental part of the American legal system ever since.