Final answer:
The missing term in the quote from Chief Justice John Marshall in Marbury v. Madison is 'judicial review.' This landmark case established the power of the Supreme Court to declare laws unconstitutional, thereby exercising a key check on the powers of the other branches of government.
Step-by-step explanation:
The most significant effect of Marbury v. Madison was that it established the principle known as judicial review. This principle, as articulated by Chief Justice John Marshall, is the power of the courts to examine the actions of the legislative and executive branches and assess their constitutionality. If a law or action is found unconstitutional, it is nullified and can no longer be enforced. The assertion of judicial review was a pivotal moment in U.S. history, strengthening the judicial branch by affirming its role as a check on the other branches of government.
During Marshall's tenure as chief justice, the Supreme Court became a central fixture in the governance process, with Marbury v. Madison (1803) serving as one of its landmark cases. The case set the precedent that the Supreme Court could declare an act of Congress unconstitutional, thereby legitimizing its power to engage in judicial review. Although William Marbury did not receive his commission, the ruling's legal impact has reverberated throughout American history, empowering the judiciary with the crucial role of constitutional arbiter.