30. The Police Commissioner may, by order in writing, prohibit any assembly or procession whenever and for so long as he considers such prohibition to be necessary for the preservation of the public peace or safety: Provided that no such prohibition shall remain in force for more than thirty days without the sanction of the Government. 31. The Police Commissioner may, by public notice, temporarily reserve for any public purpose any street or public place and prohibit persons from entering the area so reserved except under such conditions as may be specified by him.