10 U.S.C. § 978

(a) (1) The Secretary concerned shall require that, except as provided under paragraph (2), each person applying for an original enlistment or appointment in the armed forces shall be required, before becoming a member of the armed forces, to— (A) undergo testing (by practicable, scientifically supported means) for drug and alcohol use; and (B) be evaluated for drug and alcohol dependency. (2) The Secretary concerned may provide that, in lieu of undergoing the testing and evaluation described in paragraph (1) before becoming a member of the armed forces, a member of the armed forces under the Secretary’s jurisdiction may be administered that testing and evaluation after the member’s initial entry on active duty. In any such case, the testing and evaluation shall be carried out within 72 hours of the member’s initial entry on active duty. (3) The Secretary concerned shall require an applicant for appointment as a cadet or midshipman to undergo the testing and evaluation described in paragraph (1) within 72 hours of such appointment. The Secretary concerned shall require a person to whom a commission is offered under section 2106 of this title following completion of the program of advanced training under the Reserve Officers’ Training Corps program to undergo such testing and evaluation before such an appointment is executed. (b) A person who refuses to consent to testing and evaluation required by subsection (a) may not (unless that person subsequently consents to such testing and evaluation)— (1) be accepted for an original enlistment in the armed forces or given an original appointment as an officer in the armed forces; or (2) if such person is already a member of the armed forces, be retained in the armed forces. An original appointment of any such person as an officer shall be terminated. (c) (1) A person determined, as the result of testing conducted under subsection (a)(1), to be dependent on drugs or alcohol shall be denied entrance into the armed forces. (2) The enlistment or appointment of a person who is determined, as a result of an evaluation conducted under subsection (a)(2), to be dependent on drugs or alcohol at the time of such enlistment or appointment shall be void. (3) A person who is denied entrance into the armed forces under paragraph (1), or whose enlistment or appointment is voided under paragraph (2), shall be referred to a civilian treatment facility. (4) The Secretary concerned may place on excess leave any member of the armed forces whose test results under subsection (a)(2) are positive for drug or alcohol use. The Secretary may continue such member’s status on excess leave pending disposition of the member’s case and processing for administrative separation. (d) The testing and evaluation required by subsection (a) shall be carried out under regulations prescribed by the Secretary of Defense in consultation with the Secretary of Homeland Security. Those regulations shall apply uniformly throughout the armed forces. (e) In time of war, or time of emergency declared by Congress or the President, the President may suspend the provisions of subsection (a).