The Chairman of the Joint Chiefs of Staff (CJCS) is the highest-ranking military officer in the United States Armed Forces and is the principal military advisor to the President, the National Security Council, the Homeland Security Council, and the Secretary of Defense. 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 is permitted to assist the President and the Secretary of Defense in exercising their command functions.