The U.S. military judge who has been presiding over Canadian Omar Khadr's terror case at Guantanamo Bay wasn't replaced because of rulings he made, his boss said Monday.

Col. Ralph Kohlmann took the unusual step of issuing a statement about the dismissal of Col. Peter Brownback, saying it was "unrelated" to any of his cases.

"Any suggestion that my detailing of another military judge was driven by or prompted by any decisions or rulings made by Col. Brownback is incorrect," the statement said.

Brownback was replaced because the army decided in February not to extend the judge's active duty status beyond the June 29 date he was supposed to return to retirement, said Kohlmann, even though Brownback was willing to stay.

Khadr's defence lawyer, Lt.-Cmdr. William Kuebler, called the explanation "odd to say the least," given that Brownback was presiding over such a high-profile case at the naval base in Cuba, where the U.S. holds people detained in its war on terror.

Kuebler said he'll investigate the circumstances of Brownback's dismissal and ask for documents relating to the matter this week.

"This latest gaffe seriously undermines any integrity or perception of legitimacy these proceedings once possessed," he said.

The announcement about Brownback came three weeks after he threatened to halt proceedings in the Khadr case if the prosecution failed to release the Canadian's detention records.

Brownback, who has resisted setting a trial date, ordered prosecutors to supply a classified prison log by May 22 to the defence, which contends Khadr was abused and coerced into making incriminating statements.

He'll be replaced by Col. Patrick Parrish.

Pressure has been building to return Khadr to Canada from the U.S. prison camp in Guantanamo Bay, particularly since a 9-0 Supreme Court of Canada ruling said conditions under which he's been held violate U.S. and international laws.

Khadr, now 21, was captured in Afghanistan when he was 15 years old. He faces life in prison for allegedly throwing a grenade that killed a U.S. soldier, Sgt. Christopher Speer, in July 2002.