The Chairman of the Joint Chiefs of Staff (CJCS) is, by U.S. law, the highest-ranking and senior-most military officer in the United States Armed Forces[2] and is the principal military advisor to the President, the National Security Council,[3] the Homeland Security Council,[3] and the Secretary of Defense.[3][4] While the Chairman of the Joint Chiefs of Staff outranks all other commissioned officers, he is prohibited by law from having operational command authority over the armed forces; however, the Chairman does assist the President and the Secretary of Defense in exercising their command functions.[2]