Trespass Act 1980, ss 3, 4, 11
Yes. A shop is private property and the owner or manager can refuse to allow you to enter or can ask you to leave once you’re inside, so long as they don’t breach the anti-discrimination laws in doing this (see: “Discrimination”). If you stay in the shop after you’ve been told to leave, you’re committing the criminal offence of trespass.
While you’re in the shop or after you’ve left, the shop can warn you to stay out of the shop if they have good reason to think you’re likely to come back. The warning doesn’t have to be in writing. If you then go back into the shop within the next two years after the warning, this is a criminal offence. When the shop gives you a trespass warning, people sometimes call this “trespassing” you.
The courts can also give you a warning to stay out of the shop if you’re convicted of trespassing, and the same two-year ban will apply.
If you commit any of those trespass offences, you can be fined up to $1,000 or imprisoned for up to three months.
Note: If you go back into the shop after getting a trespass warning and you shoplift again, you could also be charged with “burglary,” rather than just being charged with trespass and theft. This is because you no longer have a legal right to enter the shop (unlike other members of the public).
Crimes Act 1961, s 231