These are some of the powers the police have under specific Acts to arrest a person without a warrant:
Summary Offences Act 1981, ss 39(1), 39(2)
Minor offences in the Summary Offences Act – A police officer can arrest you if they’ve got good reason to suspect you’ve committed an offence against the Summary Offences Act. This Act deals with a range of less serious crimes like common assault, tagging, disorderly behaviour, and drinking in public (some of these are covered in the chapter “Common crimes”).
Family Violence Act 2018, s 113
Breaching a family violence Protection Order – The police can arrest a person they have good cause to suspect has breached a Protection Order. (See the chapter “Family violence and elder abuse”.)
Policing Act 2008, s 36
Drunk in a public place or when trespassing – If the police find you drunk in a public place, or drunk while trespassing on private property, they can take you into police custody. They have to release you once you’ve sobered up, and can’t hold you for more than 12 hours.
Mental Health (Compulsory Assessment and Treatment) Act 1992, s 109
Mental illness – The police can take you into custody if you’re in a public place and they’ve got reasonable grounds to believe you have a mental disorder. They can take you to a police station, hospital, or other appropriate place, and arrange for a doctor to examine you as soon as practicable. See the chapter “Mental health”.