Nullification, nuhl uh fuh KAY shuhn, is the action of setting aside a law by declaring it null and void. The United States Constitution does not provide any way for a law of Congress to be declared unconstitutional after it has been signed by the President. Some delegates to the Constitutional Convention believed that the courts would naturally assume this authority. But only in 1803, with the case of Marbury v. Madison, did the Supreme Court of the United States flatly assert the right of the courts to pass on the constitutionality of an act of Congress.