The Conservative government's attempt to move an Ottawa-based judge to Quebec has become ensnared in a legal challenge, putting in doubt the judge's availability for a looming vacancy on the Supreme Court of Canada.

Justice Robert Mainville of the Federal Court of Appeal is a specialist in aboriginal issues who represented the James Bay Cree for 25 years as a lawyer. He was on the government's list of six candidates for a Supreme Court vacancy last summer, a Globe investigation revealed in May.

Federal Court of Appeal judges are not eligible for any of the three spots on the Supreme Court reserved for Quebec. In June, the government appointed Justice Mainville to the Quebec Court of Appeal, whose judges are eligible for the Supreme Court.

Story continues below advertisement

But Rocco Galati, the Toronto lawyer who toppled a judge sworn in to the Supreme Court last year, filed a challenge to that move, and in late July the Quebec government asked the province's top court to rule on the legality of the appointment. The hearings will not be held until some time in December, the Quebec Court of Appeal confirmed this week. The spot on the Supreme Court opens up on Dec. 1 after the mandatory retirement of Justice Louis LeBel, who is turning 75.

The Prime Minister could delay the appointment past December, but that would leave the court shorthanded – far from ideal, because there would be fewer judges to share the work, and because the court is required by law to have three Quebec members.

Justice Mainville was never sworn in to the Quebec appeal court.

It is not publicly known what the government intended for him. But the view was widely held in Quebec legal circles at the time that Mr. Harper was considering a Supreme Court appointment for Justice Mainville. A show of hands at a Montreal conference attended by 60 top members of the profession, including retired appeal-court judges, indicated that most thought it was on the table, while only two or three couldn't envision it happening. The Quebec justice department, while calling the possibility hypothetical, publicly expressed concern.

The government's attempt to move Justice Mainville to Quebec raised questions partly because it followed the Supreme Court's unprecedented rejection of Prime Minister Stephen Harper's appointee, Justice Marc Nadon, and a bitter public dispute between Mr. Harper and Chief Justice Beverley McLachlin.

"It's hard not to think that they were considering him, given the fact that he has a high profile and was on the list" for the previous Supreme Court opening, University of Montreal law professor Jean-François Gaudreault-DesBiens said in an interview.

The court ruled Justice Nadon ineligible after he had already been sworn in because as a member of the Federal Court of Appeal he lacked current Quebec qualifications meant to preserve the province's unique legal culture.

Story continues below advertisement

The Supreme Court was left with eight judges, one short of its usual number, for 10 months during and after the legal battle over Justice Nadon. A similar delay could be in store if the government wishes to appoint Justice Mainville.

Through a spokesperson for the Federal Court of Appeal, Justice Mainville declined comment this week. A spokesperson for Justice Minister Peter MacKay would say only that "these appointments have always been a matter for the executive and continue to be. We will respect the confidentiality of the consultation process and will not comment on specific recommendations."

Mr. Galati argues that it is illegal to appoint a Federal Court judge to the Quebec appeal court, under rules that go back to Canada's founding in 1867 which said that judges of the Quebec courts must be chosen from members of that province's bar.

"At the end of the day, the government has to know there are people out there watching," Mr. Galati said in an interview. "You don't get to spit on the Constitution."