Michael Cooke has resigned as editor in chief of the Sun-Times. The paper announced Wednesday that he’s going back to Canada to become editor of the Toronto Star, Canada’s largest-circulation newspaper, where he worked early in his career. The publisher of the Star is John Cruickshank, who used to be publisher of the Sun-Times and to run the entire Sun-Times News Group consisting of a hundred or so daily and weekly papers.

It’s not the first time Cooke’s quit the Sun-Times. He was editor in chief from 2000 to 2004, when he quit to become editor in chief of the New York Daily News. That job didn’t work out and Cruickshank brought him back to Chicago in 2005 as vice president, editorial for the news group — meaning top editor of every paper but the Sun-Times itself.

In September of 2006 Cruickshank gave him back his old job too. John Barron, who’d been the editor in chief, was given the fancy title of executive editor of the news group, which actually meant that he ran all the operations but editing. Cruickshank told me at the time that the news group needed a central administrator. “I knew that wasn’t Michael. That’s not his strength,” Cruickshank said. “I really needed John to step up to a broader management role. And it seemed silly not to give Michael full rein with all our newspapers. John did a great job, but Michael just has an enormous amount of experience. I have Michael now at the Sun-Times working on that paper on a daily basis. I have editors of all the other papers reporting to Michael.”

Cruickshank and Cooke were summoned to Chicago from Vancouver in 2000 by then publisher David Radler to run the Sun-Times together. The world turns quickly, and in the past nine years Radler has resigned under fire, pleaded guilty to corruption charges, served a prison sentence, and been released. Cruickshank left Chicago in 2007 to become publisher of the CBC. He was succeeded as publisher of the Sun-Times by his boss, Cyrus Freidheim, board chairman and CEO of the Sun-Times Media Group, which is the corporate remnant of the Hollinger newspaper empire that Radler had built up with Conrad Black (who’s still in prison).

With Sun-Times Media Group stock selling at pennies a share, a major shareholder recently revolted, and last month they forced Freidheim and other incumbents off the board of directors. Freidheim resigned from the company, and he was replaced as publisher of the Sun-Times by John Barron, the same person whom Cooke two years ago replaced as editor in chief.

“His contributions have been immeasurable,” said Barron Wednesday in a statement praising Cooke’s “exceptional flair and creativity.” Cooke said the opportunity to edit the Star was “irresistible,” and he noted that for 30 years Cruickshank has been his “friend, colleague, partner, and boss.”

Jeremy Halbreich former president and general manager of the Dallas Morning News, has succeeded Freidheim as chairman and interim CEO of the Sun-Times Media Group.