27Obstructing or failing to assist a service policemanE+W+S+N.I.
(1)A person within subsection (2) commits an offence if—
(a)he intentionally obstructs, or intentionally fails to assist when called upon to do so, a person who is—
(i)a service policeman acting in the course of his duty; or
(ii)a person subject to service law lawfully exercising authority on behalf of a provost officer; and
(b)he knows or has reasonable cause to believe that that person is a service policeman or a person exercising authority on behalf of a provost officer.
(2)A person is within this subsection if he is—
(a)a person subject to service law; or
(b)a civilian subject to service discipline.
(3)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.