Section 4(1)(a) in The Seaward Artillery Practice Act, 1949
(a)give directions prohibiting or restricting the use of the notified area or any part thereof including the use of any part of the area of the sea by any vessel, and take such further measures as may be necessary to ensure that no unauthorised person enters, passes over or remains in the notified area or part thereof, as the case may be, during such practice, and