Troy Mercanti leaving prison in a Finks gang jumper emblazoned with "violence" would be illegal under the Government's anti- association laws to be introduced soon,

Troy Mercanti leaving prison in a Finks gang jumper emblazoned with "violence" would be illegal under the Government's anti- association laws to be introduced soon, Attorney-General Christian Porter suggested yesterday.

Mr Porter said the Bill, which would allow courts to declare bikie gangs criminal organisations, was "close to being ready" and he hoped to introduce it this year.

In a display the Opposition branded attention seeking and offensive, Mercanti left Casuarina Prison on Tuesday in a Finks jumper with the club slogan "attitude" and "violence" splashed on it.

He was then greeted with bear hugs from up to eight associates wearing Finks colours.

Mr Porter said once a club was declared a criminal organisation under the laws, anti-association orders could be slapped on members to stop them meeting.

"Bikie gangs gain a lot of their force and are able to engage in a lot of their criminal practices by virtue of the fear and intimidation they create by banding together, wearing colours, being readily identifiable and this helps with a whole range of criminal activities such as standover tactics," he told ABC radio.

"If you make it a penalty for people to identify themselves with a group that's been declared a criminal organisation . . . you take away a very large part of the reason for being in a bikie gang."

Mr Porter said a High Court decision in NSW a few weeks ago paving the way for groups to be declared criminal organisations had provided a blueprint for the WA laws.

Opposition police spokeswoman Margaret Quirk said the writing on Mercanti's jumper would be offensive to the person he was jailed for assaulting in 2008.

"It's clear that prison has not had a rehabilitative effect," she said.

Ann O'Neill, director of crime victim support group Angelhands, said many victims of violent crimes would find the release of their attackers traumatic regardless of what they were wearing.

Mercanti was questioned by South Australian police when he flew to Adelaide on Tuesday night.