s 57 Arrest without warrant
57.—(1) A member may, without warrant, arrest a person over whom the member has a power of arrest if —(a) the member finds the person committing a service offence; or (b) the member suspects, on reasonable grounds, that the person is committing or has committed a service offence and believes, on reasonable grounds, that the arrest of the person without warrant is necessary —(i) to ensure the appearance of the person before a disciplinary officer; (ii) to prevent any further disturbance of a substantial nature to public order; (iii) to ensure the personal safety or wellbeing of the person; or (iv) to prevent persistence in, or a repetition or continuance of, the service offence. (2) For the purposes of this section —(a) an officer has subject to the regulations a power of arrest over —(i) a member of a lower rank; and (ii) any officer, if the officer is behaving in a disorderly or violent manner; (b) a non-commissioned officer has a power of arrest over —(i) a serviceman of a lower rank; and (ii) any serviceman, if the serviceman is behaving in a disorderly or violent manner; (c) a provost officer, or a person lawfully exercising authority under or on behalf of a provost officer, has a power of arrest over any member; and (d) a police officer has a power of arrest over a person whom the police officer suspects on reasonable grounds —(i) to be unlawfully at large during the currency of a sentence of imprisonment or detention imposed under this Act; or (ii) to be in desertion or absence without leave. (3) A power of arrest under this section may be exercised personally or by giving an order for the arrest of the person concerned, and it is the duty of the member to whom such an order is given to carry out the order.