The coming retirement of the chief justice of the Supreme Court could be seen by some as an opportunity for the prime minister to put his stamp on the institution, but experts say Canada's high court is almost impossible to steer in any given direction.

When the Supreme Court of Canada ruled in Feb. 2015 that denying a doctor-assisted death was unconstitutional, seven of the justices on the bench were appointees of former prime minister Stephen Harper.

When the same court struck down Canada's prostitution laws prohibiting brothels, living on the avails of prostitution and communicating in public with clients, five of the Supreme Court justices were Harper appointees.

"What more would Trudeau want out of a court?" asked Howard Anglin, Harper's former deputy chief of staff whose job was to advise the prime minister on whom to elevate to Canada's top court. "I don't think [Trudeau] needs to look to change the court to have the sort of court he would want."

Regionally balanced

Part of the challenge in attempting to "stack" the Supreme Court, Anglin said, is that convention in Canada dictates two of the justices have to be from the West, one has to be from Atlantic Canada, and there have to be three each from Ontario and Quebec.

That means the pool of qualified candidates for each new position on the Supreme Court is drawn from a smaller group of regional candidates.

Once the qualified candidates are narrowed down, it becomes harder to choose someone who leans politically in one direction. A reason for that, he says, is because Canadian judges are not as political as they are in the U.S.

Cabinet ministers, as we all know, come and go. But the chief justice, once appointed, will be there, bar unforeseen situations, up until mandatory retirement. - Anne McLellan, former Liberal justice minister

"I don't think the function of the Supreme Court in Canada lends itself in the same way that it does in the U.S. where judges are obviously selected differently depending on whether the Democrats or Republicans are in office," former Supreme Court of Canada justice John Major told CBC News.

Major said that in his experience justices have remained largely non-political and therefore it's almost impossible for any one prime minister to put their stamp on the institution.

"Unless the philosophy of the court changes I don't think [Trudeau] can leave a mark on it," Major added.

Choosing a new chief justice

Prime Minister Justin Trudeau has two immediate challenges. One is replacing Beverley McLachlin as the chief justice. Historically, the role of chief justice has been selected from among the remaining sitting justices, and that position almost always rotates between a justice from Quebec and the rest of Canada.

The one exception to that conventional practice is when Pierre Trudeau appointed Manitoba's Brian Dickson in 1984 to succeed Ontario's Bora Laskin as chief justice.

Justin Trudeau could decide to go that route and pick a chief justice that is not from Quebec, but as Anglin notes, when Trudeau flirted with the idea of not appointing the last Supreme Court justice from Atlantic Canada he faced widespread backlash and ended up appointing Malcolm Rowe from N.L.

Justice Malcolm Rowe takes his place at the bench of the Supreme Court during a welcoming ceremony in December. Trudeau flirted with the idea of not appointing the last Supreme Court justice from Atlantic Canada, but ended up appointing Rowe, who is from Newfoundland and Labrador. (Fred Chartrand/Canadian Press)

"I think he would do well to avoid that and indicate right away that he would follow that precedent," said Anglin.

A question of leadership

Appointing a chief justice is "the most important appointment a prime minister makes," said Anne McLellan, A former federal Liberal justice minister under prime minister Jean Chrétien. "Cabinet ministers, as we all know, come and go. But the chief justice, once appointed, will be there, bar unforeseen situations, up until mandatory retirement."

Eugene Meehan, the former executive legal officer for the Supreme Court in the early 1990s, said that in choosing the next chief justice Trudeau would serve himself and the country better by picking a strong leader.

Anne McLellan says a prime minister shapes the court by making strong merit-based appointments. (Adrian Wyld/The Canadian Press)

"It's not so much a prime ministerial stamp as an opportunity to place another solid judicial captain at the helm, to steer Canada's legal system into the decades ahead," he said.

McLellan agrees, saying the notion of putting a stamp on the Supreme Court is one not associated with Canada's legal system.

She said the way a prime minister shapes the court is by making strong merit-based appointments. She pointed to Chrétien's decision, when McLellan was justice minister, to make McLachlin Canada's first female chief justice based simply on what McLellan says was merit and competence.

A new appointment process

If Trudeau promotes one of the other Supreme Court justices to chief justice, he then has to appoint someone to fill McLachlin's empty chair, which becomes more challenging when the prime minister has to limit himself to a candidate from the West.

McLachlin is from B.C. and there is some debate, Anglin says, as to whether the two Western Canadian seats on the court should be filled with a candidate from any of the four Western provinces or if one seat is specifically for B.C and the other is for Alberta, Saskatchewan and Manitoba.

"I think he should look hard at someone from B.C. first, and only if he didn't find someone acceptable from B.C. should he look further, " said Anglin.

Complicating matters further is the new appointment process for Supreme Court justices announced in August of last year.

Former prime minister Kim Campbell is chair of an independent advisory board that recommends a short-list of three to five candidates for the Supreme Court. (Jonathan Hayward/Canadian Press)

Former prime minister Kim Campbell has been named chair of an independent advisory board that recommends a short-list of three to five candidates to the prime minister for his consideration.

Those candidates come from a pool of bilingual lawyers or judges across Canada who applied to the high court.

"Trudeau has introduced an advisory process that will limit his own discretion," said Emmett Macfarlane, author of Governing from the Bench: The Supreme Court of Canada and the Judicial Role.

"A selection committee will be recommending him a set of names for consideration, so patronage and ideology are even less likely to dominate the process."