Tamil migrants who arrived on B.C. shores last summer from Sri Lanka may have a better chance of staying in Canada after the federal government lost an admissibility hearing.

Refugee board member Marc Tessler ruled that mere association with banned terrorist group the Liberation Tigers of Tamil Eelam is not enough to prove membership in that group -- a conclusion that may make it more difficult for the federal government to send the migrants back.

"Having a definition of membership that would encompass such low-range activities was too broad to encompass membership in a terrorist group," said lawyer Eric Purtzki, who represented one of the migrants at the hearing.

The federal government has filed arguments before the board that some 30 Tamil migrants should be ordered removed from Canada based on the fact that they are members of the Liberation Tigers of Tamil Eelam, or Tamil Tigers.

In some of those cases, the government alleges it has direct evidence that some Tamils are part of the formal structure of the group, or was complicit in organizing the smuggling.

But in others, the argument hinges on whether some association with the Tigers could constitute membership.

The ruling was on the case of B173, an ethnic Tamil who cannot be identified because of a publication ban. He was accused of being a member of the LTTE because he repaired buses in a public transport company controlled by the LTTE, and in a second job repaired two vehicles belonging to the LTTE.

"He worked for a public bus transport authority where he repaired public buses as a mechanic in the village," Purtzki told CTV News.

Purtzki told the hearing that in areas where the LTTE had wide control of their territory and was involved in the daily lives of citizens, nearly everyone could be argued to be a member – which means that definition of membership is too broad.

Purtzki said alleging the mechanic was a member of the Tamil Tigers would be like saying a mechanic who fixed buses for Translink is a member of the governing party of B.C., the BC Liberals.

"If you follow the minister's logic literally everybody would be a member of the Tamil Tigers, a teacher, a nurse, or someone selling a soft drink to a soldier," he said. "In the context of daily life and because the LTTE operated a de facto state any contact with the LTTE was inescapable and unavoidable," Purtski said.

B173 also wrote on a refugee claim with the United Nations High Commissioner for Refugees that he was a member of the Tigers.

While testifying at the hearing, B173 said he lied on the refugee claim because he believed it would improve his chances of success.

492 ethnic Tamils arrived on the M.V. Sun Sea in August after the LTTE lost the civil war in Sri Lanka.

Some 70 migrants, including B173, remain in detention. B173's next detention hearing is Monday.

The ruling by Marc Tessler could be appealed to the Immigration Appeals Division or to Federal Court.

With a report from CTV British Columbia's Jon Woodward