Hells Angels is returning to court to challenge Whanganui's anti-gang patch bylaw on the grounds that the council has overstepped its powers.

Christchurch lawyers Lane Neave lodged an application in the High Court at Whanganui for a judicial review of the bylaw last week on behalf of Auckland-based member Philip Ernest Schubert.

Under a bylaw Whanganui District Council introduced last September, people wearing gang insignia in Whanganui could be fined $2000 and the insignia confiscated.

Whanganui Mayor Michael Laws is hailing a police report on the bylaw's impact, including a significant decline in prosecutions for wearing gang insignia, as a vindication of the council's tough stance.

Police estimate gang membership has dropped by 15 per cent in Wanganui as a result of the council ban on patches and strong police anti-gang operations.

However, Mr Schubert has applied for a judicial review on the grounds that the council has gone beyond the limits imposed on it by a bill passed in Parliament in May last year banning wearing of gang insignia in public places in Whanganui.

"The law contemplated distinct, specified areas - they've just gone for an all-encompassing quarantine zone in effect around Whanganui," Lane Neave solicitor Steven Rollo told NZPA.

The council had ringfenced the whole of Whanganui and each settlement on all the highways approaching the city.

"In a literal sense that is not the council's entire district, but the effect is that as a matter of law that is total prohibition across council's entire district, because where else are you going to wear gang insignia?" Mr Rollo said.

The application also said the council was not empowered to pass a bylaw in breach of the Bill of Rights.

The council has about six weeks to respond, and the court then decides how quickly to proceed.

In June, a Hastings member of the Hells Angels lost a district court challenge after he was prosecuted for wearing a Hells Angels t-shirt outside Whanganui police station within a week of the bylaw coming into force.

"It is little wonder gangs want to challenge our law," Mr Laws said today.

"The police report makes it clear that it is working and that it has become very uncomfortable to be a gang member in Whanganui."

Local Government New Zealand wanted Parliament to allow all councils to follow Whanganui, he said.

Police believed the bylaw was acting as an effective deterrent and had contributed to:

* overt gang presence being less noticeable by the general public

* a reduction in levels of intimidation for the community

* a reduction in confrontations between gangs.