s 20 Unfitness or misconduct through alcohol or drugs
(1) A person subject to service law commits an offence if, due to the influence of alcohol or any drug— (a) he is unfit to be entrusted with his duty or any duty which he might reasonably expect to be called upon to perform; or (b) his behaviour is disorderly or likely to bring discredit to Her Majesty's forces. (1A) For the purposes of subsection (1) a person is to be taken to be unfit to be entrusted with his duty, or a duty which he might reasonably expect to be called upon to perform, if his ability to carry out the duty in question is impaired. (2) Subsection (1) does not apply to the influence of a drug on a person (“A”) if— (a) the drug was taken or administered on medical advice and A complied with any directions given as part of that advice; (b) the drug was taken or administered for a medicinal purpose, and A had no reason to believe that the drug might impair his ability to carry out the duties mentioned in subsection (1)(a) or (as the case may be) result in his behaving in a way mentioned in subsection (1)(b); (c) the drug was taken on the orders of a superior officer of A; or (d) the drug was administered to A on the orders of a superior officer of the person administering it. (3) In this section— (a) “ drug ” includes any intoxicant other than alcohol; (b) a person's “ behaviour ” includes anything said by him. (4) In proceedings for an offence under this section, any paragraph of subsection (2) is to be treated as not having applied in relation to the defendant unless sufficient evidence is adduced to raise an issue as to whether it did. (5) A person guilty of an offence under this section is liable to any punishment mentioned in the Table in section 164, but any sentence of imprisonment imposed in respect of the offence must not exceed two years.