The Canadian wing of an international Jewish organization wants Prime Minister Justin Trudeau to send government lawyers to join the legal fight against Quebec's secularism law.

B'nai Brith Canada published an open letter Thursday after a Quebec Superior Court justice denied a request to freeze the most controversial parts of the law, formerly known as Bill 21.

The bill blocks civil servants in positions of authority, such as teachers, police officers and Crown prosecutors, from wearing religious symbols, such as hijabs or kippahs, on the job.

The National Council of Canadian Muslims and the Canadian Civil Liberties Association are challenging the law on constitutional grounds — a task made more challenging by the Quebec government's invocation of the Charter's notwithstanding clause.

"We felt it was necessary to send out a letter to the prime minister immediately, because this is an issue that affects not just Quebec, but all Canadians from coast to coast," said Harvey Levine, director of the Quebec arm of B'nai Brith Canada.

Harvey Levine is the regional director of B'nai Brith in Quebec. He says all Canadians are potentially affected by the secularism law. (Sarah Leavitt/CBC)

The prime minister, along with Conservative Leader Andrew Scheer and NDP Leader Jagmeet Singh, all say they do not support the law. But no party has come forward to back a legal challenge.

The group, which describes itself as a defender of Israel that combats racism and anti-Semitism, argues the federal government should immediately intervene.

B'nai Brith argues it has an impact on those elsewhere in the country who may be considering moving to Quebec, and it wants to see Trudeau take a harder line against the law.

"The election is not really our issue," said Levine. "The issue is standing up for minority rights, for minorities right across Canada."

Court battle continues

Robert Leckey, dean of McGill University's faculty of law, says the rejected injunction doesn't change the stakes at the federal level.

"The substantive challenge of the law will still move forward," Leckey said.

He said the federal government could still intervene, either as the case is in Quebec Superior Court or if it gets appealed later.

"I suspect it wouldn't be too late to try that after the federal election, if they wanted to keep their heads down until then," he said.

Quebec could be major battleground

Shachi Kurl, executive director at the Angus Reid Institute, says there's still time before the federal election and that a lot can happen before voting day, but at this point taking a strong stand "has the potential to be more of a political loser for any federal party leader, other than the Bloc [Québécois] leader, than a political winner."

Conservative Leader Andrew Scheer will have to navigate the issue carefully since he has supporters on both sides of the issue. (Sean Kilpatrick/Canadian Press)

With the race currently looking tight, federal leaders are likely weighing the cost of being seen to step into provincial jurisdiction.

Trudeau taking further action would "become something of a minefield for him," Kurl said.

"Does he really want to be another Trudeau who starts getting into it with Quebec on jurisdiction issues?" she said. "No, he does not."

Kurl said that coming out strong against the law is also a challenge for Scheer, as he has supporters on both sides of the issue.

"He's also spoken out against Bill 21 — but he's got to be careful. Because outside of Quebec a significant amount of his base, and indeed what base he has inside Quebec, is a base that likely is supportive of Bill 21," she said.

In Alberta, Saskatchewan and Manitoba, polling data suggests a sizeable minority — 45 per cent in Alberta — supports a similar law being imposed on home turf.

"Scheer has to be careful not to alienate those segments," she said.

Kurl added that if one party is clearly ahead in British Columbia or Ontario, you may see them come out stronger against Bill 21.

But "if all of a sudden Quebec becomes a real battleground … we will have to see how [Trudeau] walks that line," she said.