Open this photo in gallery Peter Hogg, seen here on Sept. 24, 2003, was considered so authoritative and trustworthy that judges were known to consult him during their private deliberations on cases. DEBORAH BAIC

He was an invisible hand shaping Canada.

Peter Hogg, a New Zealander who became this country’s pre-eminent constitutional scholar, was sometimes called the 10th person on the nine-member Supreme Court of Canada.

A textbook he wrote, Constitutional Law of Canada, published in five editions and updated annually in a loose-leaf version, is the work most cited by the court, found in a remarkable 190 decisions – the first in 1979, the most recent on Friday.

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“The law is what the judges say it is, but Peter had a big role in telling the judges what to say,” retired Supreme Court judge Ian Binnie (1998-2011) says.

“His contribution is now baked into the minds of generations of law students, lawyers and judges – his work dominates Canadian thinking about the constitution whether we recognize it or not.”

A law professor and dean, Mr. Hogg was from far from an ivory-tower scholar. He advised a wide array of clients, including several governors-general, First Nations groups, and the Ontario, federal and Alberta governments. He also addressed parliamentary committees on wide-ranging matters of law, beginning in 1978, with his final such appearance coming last year, on a bill affecting Indigenous children. And he was an experienced advocate, appearing numerous times in the Supreme Court, where “he relished facing down nine interrogators,” Mr. Binnie said, “like a chess master simultaneously playing multiple opponents.”

The man who quietly shaped Canada had a conventional, affluent upbringing. Peter Wardell Hogg was born on March 12, 1939, in Lower Hutt, near Wellington, N.Z., the son of Eric Hogg, a lawyer, and Mary Hogg (born Wardell), a homemaker. At primary school, where some Maori pupils attended in bare feet, he and his younger sister Margaret would take their sandals and socks off when they left their house and hide them in a hedge, in sympathy with the barefoot children, his sister, Margaret Carr, recalled.

As was typical in affluent homes, his parents sent him to a boys’ boarding school, Nelson College, for secondary education. He found it oppressive, his son, David, a professor of astrophysics at New York University, said. “He liked to say, everything was either compulsory or forbidden. The days were scheduled down to the minute, including the time on Sunday afternoons in which they had to write a letter home of a specified length.”

From that experience, he developed a lifelong sense of discipline. He wrote that weekly letter home into his 60s, eventually addressing it to his own family. He was a creature of habit, David said. “Every day he did a little bit of work toward the revision of the book. He got up at the same time, he came home at the same time. He had a nice dinner and would do 45 minutes of work.”

After studying law at the University of New Zealand (now Victoria University of Wellington), he joined his father’s downtown law firm, where a colleague noticed his academic bent, and suggested he apply for a U.S. scholarship. His father told him it was a waste of time – he could be making money – but he went off to Harvard, where he obtained a master’s degree in law.

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It was at Harvard that he met Frances Benson, a self-described “pepper-pot” from Baltimore, who was studying for her master’s in education. The cafeteria was full of strangers; one space remained next to a young man she knew. “I thought he had the funniest accent I ever heard, so I kept trying to make him talk,” Ms. Hogg said. They would be married for 53 years.

He took a teaching job at Monash University in Melbourne, where he received his PhD in law in 1970, but the school was rigid and hierarchical, modelled after British schools. Osgoode Hall, which had recently joined up with York University in Toronto, was more open to new ideas and people. Gerald Le Dain, a future Supreme Court judge, was the dean. Mr. Hogg came to Osgoode in 1970, and became a citizen in 1975.

He was skeptical when Mr. Le Dain asked him to teach constitutional law. "I said ‘Gerry, I know nothing about Canadian constitutional law,’” he told Virginia Corner, who interviewed him for an Osgoode publication. “He said ‘I have four sections to staff, and I only have professors for three of them.’”

The notes he made for his lectures became the first edition of his book, a slim volume that came out in 1977.

His second edition, published in 1985, three years after the Charter of Rights and Freedoms took effect, was double in size. And the third edition, published in 1992 in a loose-leaf edition, doubled that one. By the fourth edition, in 1997, it had grown to 1,400 pages.

The book, close friend John Evans says, was like its author: “balanced, sensible and middle-of-the road.” Its synthesis of Supreme Court judgments gave it a magisterial quality, in the best tradition of British textbooks, he said.

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“Judges loved his writing because it made the law seem more coherent than perhaps it was,” Mr. Binnie said. “On the rare occasions when the Supreme Court disagreed with Peter’s view, the judges usually felt it necessary to explain their side of the disagreement, perhaps in an effort to forestall a devastating riposte in the next edition of his book.”

So authoritative and trustworthy was he considered that judges were known to consult him during their private deliberations on cases.

Mr. Evans said that while he suspects Mr. Hogg gave confidential advice to Supreme Court judges, “I know for a fact judges on other courts have reached out to him.” Mr. Evans is a retired Federal Court of Appeal judge. (He said it was other judges, not Mr. Hogg, who told him.)

Once Mr. Hogg argued against his own book on behalf of a client, and a Supreme Court judge asked him which source they should believe. “It was hilarious,” said Mary-Ellen Turpel Lafond, a lawyer and former Saskatchewan judge, who witnessed the incident.

In his decades at Osgoode, including a reluctant five-year stint as dean from 1998 to 2003, he was a legendary teacher, Mr. Evans said, “respected, admired and revered in a way that I think no one else was.” Mr. Evans went to some classes himself “to see what the Hogg magic was.”

The secret lay in his personal qualities. “Students knew he was on their side. He was there to help them learn the law. He was not there to show how brilliant he was and how ignorant they were. He wasn’t there to make it so complicated that only minor geniuses could possibly unravel it, or people who spent as much time thinking about it as Peter Hogg did.”

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As much as he was respected for his legal wisdom, and honoured as a Queen’s Counsel and a companion of the Order of Canada, he was regarded with deep affection for a gentle, modest, kind, optimistic and generous nature. When lawyer Allison Thornton was a first-year student, she went to work for him as a researcher, and says he treated her as a peer. The next year, rather than bury her contribution in a footnote, he credited her with joint authorship (under her birth name, Bushell), on one of his most widely read journal articles – the constitutional “dialogue” between the courts and Parliament. For the next quarter-century, he was her mentor.

“I didn’t know how much I was going to get out of an $11-an-hour job. It was a lifetime of support and encouragement and inspiration,” she said.

Two cases stood out for him as special accomplishments. One involved advising the Council of Yukon Indians (now called the Council of Yukon First Nations) in successful land-claims and governance talks with Ottawa and the Yukon, culminating in agreements in the early 1990s. His credibility had a big impact on the other parties, recalls Dave Joe, a lawyer from the Champagne and Aishihik First Nations.

“It was like getting Connor McDavid to play for your team.” He added that Mr. Hogg felt Canada had a responsibility to ensure space in its Constitution for Indigenous peoples.

Another came in 2004 when he was lead counsel for the federal attorney-general in an important case for same-sex marriage at the Supreme Court.

“That’s the case I’m most proud of because I think that really increased the sum of human happiness,” he told Ms. Corner.

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In 2006, Mr. Hogg proved himself indispensable in Canada’s first-ever public hearing for a Supreme Court nominee, created by prime minister Stephen Harper.

First, Mr. Hogg gave the nominee, Marshall Rothstein, a three-hour crash course in constitutional law; and then, he oversaw the hearing itself, instructing parliamentarians on what kinds of questions they could ask Mr. Rothstein.

“He was a masterful teacher,” Mr. Rothstein said. “That wasn’t easy stuff. He was able to convey it to me in such a coherent, concise way. It was everything that I needed.”

But why, as such a respected legal authority, was he never put on the Supreme Court? Other law-school professors have reached the court, such as current members Russell Brown and Nicholas Kasirer, and the late chief justice Bora Laskin. But all three did stints on provincial courts of appeal first. Mr. Hogg turned down such a job, according to both David and Ms. Hogg, because he preferred teaching and did not want the grind of the appeal-court job.

David recalls a period when his father was excited, thinking he had a chance to be appointed to the Supreme Court. But Anne McLellan, a former justice minister, says she does not recall his name being on a short-list for two Supreme Court vacancies, one in 1998, and the other in 1999 (Mr. Binnie and Louise Arbour, a former Osgoode colleague, were appointed), around the time he was turning 60, the prime age for a new appointee.

After he left Osgoode, just short of mandatory retirement age, he became a scholar-in-residence at Blake, Cassels & Graydon, a national law firm. “Every Supreme Court factum [written argument] I’ve done in my life I’ve always run past Peter,” Brad Berg, a senior lawyer at the firm, said. (Once, when Mr. Berg lost a case 9-0, Mr. Hogg dropped his habitual modesty, telling him: “The Supreme Court got it wrong.”)

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Mr. Hogg died of bleeding on the brain late in the night of Feb. 4, leaving his wife, Ms. Hogg; his adult children, David and Anne; a granddaughter, Vera; and his sister, Margaret Carr of New Zealand. He was 80.