New South Wales Consolidated Acts(cf Crimes Act 1900 , s 352, Cth Act, s 3W)
(1) A police officer may, without a warrant, arrest a person if:(a) the person is in the act of committing an offence under any Act or statutory instrument, or(b) the person has just committed any such offence, or(c) the person has committed a serious indictable offence for which the person has not been tried.
(2) A police officer may, without a warrant, arrest a person if the police officer suspects on reasonable grounds that the person has committed an offence under any Act or statutory instrument.
(3) A police officer must not arrest a person for the purpose of taking proceedings for an offence against the person unless the police officer suspects on reasonable grounds that it is necessary to arrest the person to achieve one or more of the following purposes:(a) to ensure the appearance of the person before a court in respect of the offence,(b) to prevent a repetition or continuation of the offence or the commission of another offence,(c) to prevent the concealment, loss or destruction of evidence relating to the offence,(d) to prevent harassment of, or interference with, a person who may be required to give evidence in proceedings in respect of the offence,(e) to prevent the fabrication of evidence in respect of the offence,(f) to preserve the safety or welfare of the person.
(4) A police officer who arrests a person under this section must, as soon as is reasonably practicable, take the person, and any property found on the person, before an authorised officer to be dealt with according to law.