Chief Justice Wagner speaks alongside his fellow justices at the Supreme Court of Canada in Ottawa in October, 2025.Sean Kilpatrick/The Canadian Press
The Supreme Court of Canada, in a rare decision, on Friday annulled the 2025 federal election result in a riding near Montreal that had been decided by a single ballot.
The top court has not annulled an election result in recent decades. In 2012, it considered that option in a similar case but narrowly decided against the move.
The latest ruling means there will be a by-election in the riding of Terrebonne.
Last April, Liberal Tatiana Auguste edged out Bloc Québécois candidate Nathalie Sinclair-Desgagné. The surprise by-election in Terrebonne emerged as the federal government is set to call two by-elections in Toronto. The Liberals have a large minority in the House of Commons.
The Supreme Court heard arguments in the Terrebonne case on Friday morning and then delivered its decision from the bench after a period of deliberation. The top court usually doesn’t decide a case the day of a hearing and instead issues judgments in the following months.
In the Terrebonne case, the court said it would deliver its legal reasoning at a later date.
“A majority of the justices of this court grant the appeal,” Chief Justice Richard Wagner said in French in the court’s briefly stated oral judgment. “We declare the annulment of the federal election of April 28, 2025, in the riding of Terrebonne.”
After last April’s election, a voter in Terrebonne said that she had cast her ballot for the Bloc, by mail. In a court summary of the case, she told media that her special ballot had been returned to her after election day, marked return to sender. What happened was an error in the postal code of the polling station that the returning officer had put on the prepaid envelope.
Supreme Court delivers expansive view of mobility rights, but says COVID-19 rules reasonable
Ms. Sinclair-Desgagné’s challenge of her one-vote defeat was first rejected by the Superior Court of Quebec last October.
Julius Grey, her lawyer, said on Friday afternoon that it was a surprise to hear the Supreme Court decision from the bench after the hearing. He said the eventual legal reasoning will be a valuable addition to the history of election results contested in the courts.
“It’s important to make certain that in any election the result is really the person who won,” said Mr. Grey in an interview. “Of course, it’s never perfect but courts should not hesitate. An election should be redone if it hasn’t produced a real winner.”
Academic experts who follow the Supreme Court closely say Friday’s annulment is a first in modern times, but likely isn’t a first since Confederation in 1867.
“I doubt this is the first time the Supreme Court has confirmed the annulment of an election result,” said Philip Girard, a leading legal historian and law professor emeritus at Osgoode Hall at York University. “In the later 19th century and the early 20th, election results used to be contested all the time.”
The last major Supreme Court case that weighted a potential annulment of an election result in a federal riding happened in 2012, after the 2011 federal election.
Ted Opitz, a Conservative, won the riding of Etobicoke Centre by 26 votes. The runner-up, Liberal Borys Wrzesnewskyj, sought to have the result annulled based on irregularities that he contended affected the result. The Ontario Superior Court of Justice granted Mr. Wrzesnewskyj’s application.
But the Supreme Court disagreed. The top court in a 4-3 decision upheld the initial election result and Mr. Opitz’s narrow victory.
In an assessment of the votes, the court’s majority found that the number of disqualified votes determined by the lower courts wasn’t enough to overturn the election result. The court said the “application to annul the election should be dismissed.”
The dissent, however, written by then-chief-justice Beverley McLachlin, disagreed and concluded that the election result should have been annulled.
Judges must speak out to bolster public confidence in courts, Chief Justice Glenn Joyal says
Then-Supreme-Court-justice Marshall Rothstein co-wrote the majority judgment in the Opitz case. In an interview on Friday after the Supreme Court ruling in Terrebonne, Mr. Rothstein said there is always a particular pressure on the top court in such instances, with an election result hanging in the balance, to produce a decision quickly.
In 2012, the Opitz case was heard in July, something that does not often happen. The decision was released about three months later. It took some time, because of the narrow split at the court, said Mr. Rothstein.
“One thing I remember vividly is it had to be dealt with urgently,” he said. “We were scrambling.”
Mr. Rothstein, who is a lawyer at Osler in Vancouver, said the importance of a swift result is probably the reason the Supreme Court on Friday delivered its decision from the bench.
“My inclination is it would be a fairly substantial majority,” he said. “The court probably was fairly decisive and felt confident in stating the result today with reasons to follow.”
Terrebonne in its current form exists since 2015 and had since then been held by the Bloc until last spring. Ms. Sinclair-Desgagné held it from 2021 to last year.
There are currently 340 members in office in the House of Commons, with an additional three vacant seats. A total 168 sitting MPs are Liberals, 142 are Conservatives, and 22 are members of the Bloc Québécois. There are seven New Democrats, and there is one member of the Green Party.
Matteo Rossi, a Liberal spokesman, said in a statement: “Tatiana Auguste ran a strong campaign, and whenever the by-election gets called, we are ready to engage with voters in Terrebonne.”
Bloc Québécois president Suzanne Proulx in a statement said: “The voters of Terrebonne will finally be able to make their voices heard.” She added that a new election should be held without delay.
Matthew McKenna, a spokesperson for Elections Canada, said the organization is ready to administer a by-election in Terrebonne.