Open this photo in gallery Prime Minister Justin Trudeau speaks with members of the Manitoba Federation of Labour (MFL) in Winnipeg on March 26, 2019. JOHN WOODS/The Canadian Press

The core question in the SNC-Lavalin affair is whether Justin Trudeau and his advisers respect the rule of law.

The answer appears to be that they have no respect for it at all, after an unnamed source, in an effort to smear former attorney-general Jody Wilson-Raybould, fed reporters a story about a dispute over choosing a judge for the Supreme Court.

Even Liberals are furious over the leak to The Canadian Press and CTV, presumably from someone inside the Trudeau government.

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“It is outrageous that there is a leak with respect to the Supreme Court judicial appointment process,” Toronto Liberal MP Nathaniel Erskine-Smith told the House of Commons ethics committee on Tuesday. “People from all parties ought to condemn that kind of thing.”

According to the reports, Ms. Wilson-Raybould recommended appointing Manitoba judge Glenn Joyal to the Supreme Court as chief justice in 2017, but Mr. Trudeau vetoed the recommendation because he thought Justice Joyal brought too conservative an interpretation to the Charter of Rights and Freedoms.

The implication from the leaker: Mr. Trudeau rightly began to question the judgment of his attorney-general long before the issue of whether to prosecute SNC-Lavalin emerged.

Related: Wilson-Raybould backed Joyal for chief justice of Supreme Court as part of broader plan

Members of the Liberal old guard are not pleased. The leak “involved extremely confidential information about applicants to the Supreme Court,” tweeted Penny Collenette, who was director of appointments for four years under Prime Minister Jean Chrétien. “Shockingly bad form.”

“Agree,” replied Senator Percy Downe, who served as Mr. Chrétien’s chief of staff. “Appalling behaviour.”

The leak certainly didn’t go down well with Justice Joyal, who is Chief Justice of Manitoba’s Court of Queen’s Bench. Immediately after the story broke, he issued a statement saying that, in fact, he had withdrawn his name from consideration for the Supreme Court after his wife was diagnosed with cancer. (In the end, Alberta appellate court judge Sheilah Martin was named to the Supreme Court and Richard Wagner of Quebec was made Chief Justice.)

“I fear that someone is using my previous candidacy to the Supreme Court of Canada to further an agenda unrelated to the appointment process," Justice Joyal protested. "This is wrong.” That’s an understatement.

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Whataboutists often invoke what they consider the misdeeds of Stephen Harper in response to criticism of Mr. Trudeau. But the Conservative prime minister never did anything like this.

In 2013, Mr. Harper openly criticized Beverley McLachlin, saying the then-chief justice of the Supreme Court had made an “inadvisable and inappropriate” attempt to contact him regarding a judicial appointment. More than 650 lawyers wrote to protest this act of political interference in the judicial process, and they were right. Mr. Harper had undermined the separation of executive and judicial power by criticizing the chief justice.

This is worse: a deliberate leak to the media about private discussions between an attorney-general and a prime minister over a judge under consideration for the Supreme Court, with the leak intended to debase the reputation of the former attorney-general. Anyone now under consideration for a judgeship will have reason to fear that their application, too, could be leaked. The legal community should be on its hind legs over this.

And then there is the question that so often gets asked of this government in the SNC-Lavalin affair: What in heaven’s name were they thinking?

At the root of this scandal is the allegation that Mr. Trudeau and his advisers interfered in the rule of law by persistently pushing Ms. Wilson-Raybould to override her own Director of Public Prosecutions and grant a plea deal to SNC-Lavalin.

Now the Prime Minister’s Office appears to have made that alleged interference so much worse, by apparently slinging mud at a political opponent by leaking a story about the Supreme Court selection process.

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How much longer will Justin Trudeau be able to keep his caucus and party together, after committing so many missteps? How much more political damage is he willing to sustain to prevent Ms. Wilson-Raybould and Jane Philpott, who also resigned from cabinet in protest, from talking about the cabinet shuffle that eventually led to their resignations?

How much more damage to the integrity of this country’s legal system is this Prime Minister willing to inflict, in his efforts to discredit these enemies he used to call friends?