"Will no one rid me of this turbulent priest?" raged Henry II when Thomas Becket caused him grief. Stephen Harper must be feeling the same way about Canada's judges.

The courts have dealt the Prime Minister one blow after another, including this week's ruling that Ottawa must hand over the Quebec names on the now-defunct long gun registry to that province's government, so that it can create its own list.

But while some trusty barons rode off to dispatch the Archbishop of Canterbury for Henry, the Prime Minister has little ability to stack the courts with sympathetic judges inclined to rule in his favour.

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In particular, there is virtually no chance that Mr. Harper's next choice for the Supreme Court, which should be announced any day now, will be a fire-breathing Tory.

The system, which produces one of the most talented and impartial supreme courts in the world, won't let him.

The Canadian prime minister, like the American president, has unfettered power to choose judges. But while the president's choice must be approved by the Senate, resulting in pitched partisan battles, the constraints on a prime minister are both more informal and more powerful.

To replace Madam Justice Marie Deschamps, who retired in August, Justice Minister Rob Nicholson consulted the Quebec attorney-general and the provincial bar association, and will likely have had conversations with several judges about what the court needs as a replacement. (The Constitution requires that at least three Supreme Court judges be from Quebec, and Ms. Deschamps was one of them.)

He submitted a list of seven candidates to a committee consisting of three Conservative MPs, one NDP MP and one Liberal MP. They narrowed the list to three, which they submitted to Mr. Harper without stating any preference.

While Françoise Boivin, the NDP MP who sat on the committee, was careful not to divulge any of the panel's deliberations, she did say in an interview that "I was very, very happy with the lack of partisanship" she found.

Some observers have detected a subtle drift of the court toward a more conservative bent – in the cases chosen or rejected for review, and in the terms of reference the court sets for itself.

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But Ms. Boivin said she could detect no conservative bias in the seven candidates from which her committee was asked to create a shortlist.

Mr. Harper's choice will appear before a parliamentary committee for questioning, though the committee will have no power to veto that choice.

The combination of private consultation, cross-party co-operation and public scrutiny ensures that no overtly partisan candidate ever makes it onto the Supreme Court bench.

This is why, although Mr. Harper has appointed four (soon to be five) judges to the court, it remains ideologically independent.

Judges picked by Mr. Harper were part of a unanimous ruling that federal proposals to create a national securities regulator were unconstitutional. The court also unanimously decided the Insite drug clinic in Vancouver should be kept open, despite the Harper government's determined efforts to close it.

The Supremes are likely to have the final say on the ruling by Mr. Justice Marc-André Blanchard of the Quebec Superior Court that the federal government may not destroy the Quebec portion of the now-defunct long gun registry, and must hand the names of that registry over to the provincial government.

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Mr. Harper once assured Canadians that those who feared he had some radical agenda could take solace in knowing he would be checked by the Senate, the bureaucracy and the courts.

The Senate is now dominated by Conservatives and the senior ranks of the public service have been shuffled repeatedly. But the courts are still there, and one out of three ain't bad.

Of course, Mr. Harper could always dispense with convention and appoint, say, Maxime Bernier, Minister of State for Small Business and Tourism, to the court. At lower levels, such things aren't unheard of. Rumours abound that Public Safety Minister Vic Toews is on his way to the Manitoba bench.

But at the highest level, a similar display of overt partisanship would be greeted with such genuine fury from the legal community, provincial governments and opposition politicians that no prime minister would ever take the risk.

Mr. Harper can do nothing about his turbulent judges, except appoint another one and grin while he does it.