Expecting prostitutes to mount an expensive and lengthy constitutional challenge of Canada's prostitution laws places an unfair burden on a group already made vulnerable by those very laws, says a lawyer helping to launch such a case.

Katrina Pacey of Pivot Legal Society, which is heading the case, says it's unfair to require working prostitutes to take on such a complex legal issue.

Former sex worker Sheri Kiselbach and a group that represents street prostitutes are attempting to challenge the laws that outlaw prostitution, arguing they push the industry into the shadows and make the lives of women in the sex trade more dangerous.

Last year, a B.C. Supreme Court judge ruled that neither Kiselbach nor Downtown Eastside Sex Workers United Against Violence have legal standing to launch a constitutional challenge because they aren't currently facing criminal charges.

The groups are currently in court appealing that decision.

"We say that (Kiselbach's) 30 years of experience in sex work should qualify you for a challenge to laws that criminalized you for 30 years," Pacey said Thursday outside of the B.C. Court of Appeal.

"You have sex workers who are subject to criminal laws, are seriously marginalized, suffer incredible discrimination and stereotyping. For them to come forward and participate in a major legal proceeding is very difficult."

On Thursday, three groups that support the challenge -- the B.C. Civil Liberties Association, the Trial Lawyers Association of B.C. and the West Coast Legal Education and Action Fund -- were granted intervener status in the appeal, to be heard in November.

If successful, the original challenge could head back to B.C. Supreme Court. If not, Pacey said the next step would be to appeal to the Supreme Court of Canada.

Kiselbach, 58, was involved in the sex trade for three decades and now works with a prostitution advocacy and support group in Vancouver's Downtown Eastside.

She said prostitution laws forced her into unsafe situations that ended with her in being assaulted and raped, making it difficult for her to go to police when she was victimized.

"I kept all the violence that I experienced hidden, I didn't feel safe to go to the police and talk to them about it," said Kiselbach.

"I don't think I was allowed to work safely, I had to always watch where I was. I couldn't just go into my apartment and do it there feeling that I was safer there, when in fact it was against the law to do so."

And, she said, when she did come forward, prostitution laws only stigmatized her further and meant her complaints weren't taken seriously.

The ruling that said Kiselbach couldn't mount a constitutional challenge came down last December, after the federal government argued she didn't have the right to participate in such a case.

Judge William Ehrcke said Kiselbach didn't have direct standing because she isn't currently facing criminal charges.

Kiselbach's past prostitution-related convictions are irrelevant now, he said, because Kiselbach could have appealed them at the time but didn't.

The judge also said Kiselbach and Downtown Eastside Sex Workers United Against Violence didn't have public-interest standing, which allows people or groups who aren't facing a legal case to still challenge the constitutionality of laws.

In his written ruling, Ehrcke said the case fails to meet one of the requirements for public-interest standing -- that there must be "no other reasonable and effective way to bring the issue before the court."

He said there are cases before B.C. courts and elsewhere of sex workers facing criminal charges, and any of them could challenge the constitutionality of the laws.

Ehrcke also noted there are legal challenges before other courts addressing the same issue, notably one in Ontario that involves at least one woman who is facing prostitution-related charges.