Tough NSW anti-bikie legislation designed to break up motorcycle gangs has been struck out by the highest court in the land because it undermines the integrity of the state's Supreme Court.

A High Court full bench ruling, handed down on Thursday, declared NSW's Crimes (Criminal Organisations Control) Act invalid and ordered the state to pay the full legal costs of the case.

It follows a successful challenge by prominent Sydney Hells Angels Motorcycle Club member Derek Wainohu, who faced the possibility of being banned from associating with his fellow club members because of the laws.

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Former Labor premier Nathan Rees introduced the anti-bikie law in April 2009, several weeks after the death of Anthony Zervas, who was killed in a bikie brawl at Sydney Airport.

The law empowered Supreme Court judges, after a request by the police commissioner, to declare individual bikie gangs criminal organisations and then ban certain members of the gangs from associating with one another.

It also granted the power to ban "controlled members" from working in certain jobs, with penalties of up to five years in jail for those who disobeyed.

But Thursday's ruling showed that the High Court judges agreed with Mr Wainohu's argument that the law undermined the Supreme Court by effectively bypassing its normal procedures.

The concerns included the lack of any right for defendants to appeal decisions made under the act, the provision for hearings to be held in private and the lack of regard for the normal rules of evidence.

"An eligible judge may make a determination ... upon information and submissions, without regard to the rules of evidence, partly based on information and submissions not able to be disclosed to the organisation or its members, and with no obligation to provide reasons for the determination which is made," the court's written judgment said in its description of the act.

"The act thus provides for the enlistment of judges of the Supreme Court to determine applications for declarations using processes which, if adopted by the court itself, would be repugnant to the judicial function."

Mr Wainohu launched his challenge to the bikie law after police applied to the Supreme Court in July 2010 asking a judge to declare the Hells Angels an outlaw organisation.

The court judgment says Mr Wainohu was at risk of being made subject to a control order, had the declaration been granted.

Mr Wainohu also raised concerns about individuals' freedoms being impinged under the law.

His lawyer, Wayne Baffsky, said the ruling was a victory for all the people of NSW, not just motorcycle gangs.

"We're very, very happy," Mr Baffsky told AAP.

"It's not just for them (Hells Angels), it's for the people of NSW.

"Because the extent of the law was extraordinary.

"It was a frightening act in my opinion that targets two or more people."

Greg Hirst, spokesman for the Brotherhood Christian Motorcycle Club, who helped raise money to fund the legal challenge, also welcomed the ruling.

"Our club is pleased with that result because we believe that the legislation was exceedingly dangerous for the whole of Australian society," he told AAP.

"Our club wholly endorses the importance of governments to address law and order issues, particularly violence, but this is about inappropriate legislation ... that takes away the rights, responsibilities, freedoms of general Australian citizens."