GUANTANAMO BAY U.S. NAVAL BASE, Cuba (Reuters) - A Canadian teen charged with killing a U.S. Army medic in Afghanistan told a Guantanamo war crimes tribunal on Wednesday that he was being unfairly punished and would no longer participate.

Omar Khadr, 19, who the U.S. military says was trained by the al Qaeda militant group, told the court he was being punished for exercising his rights but did not elaborate. His military lawyer, Lt. Col. Colby Vokey, angrily said Khadr had been moved to solitary confinement "for no reason whatsoever" on March 30, making it difficult to prepare a defense.

"I say with my respect to you and everybody else here that I am boycotting these procedures until I (am) treated humanely and fair," the Toronto-born Khadr told the presiding officer during his pretrial hearing at the U.S. naval base in Guantanamo Bay, Cuba.

Khadr spoke softly but Vokey shouted and slapped the table during a heated argument with the presiding officer, Marine Col. Robert Chester, who recessed the hearing and asked to see Vokey in private.

The hearing resumed later under protest from the defense attorneys. They said it was an ethical violation for them to continue after their client asked them to take no further action until the solitary confinement ended. Chester said he would take up the issue later in the week.

Khadr remained in the courtroom and answered "Yes, sir," when Chester asked if he understood certain rights.

Khadr's father, Ahmed Said Khadr, an al Qaeda financier and close friend of Osama bin Laden, moved his family between Canada, Pakistan and Afghanistan and sent his son to al Qaeda training camps to learn how to use guns, grenades and explosives, the U.S. military has said.

The elder Khadr was killed in a shootout with Pakistani security forces in 2003.

His son's hearing began with a testy exchange over who had authority to grant Khadr's request for a Canadian lawyer to join the defense team. Chester said he would decide if he had that authority, once Vokey made the request in writing.

Vokey retorted that the tribunal rules were unclear and not based on any legal framework, a common complaint from military lawyers assigned to defend the 10 Guantanamo prisoners charged before the tribunals.

"There's no precedent here," Vokey fumed. "I don't know what rule to look to. I don't know what law to look to."

Pentagon officials said the tribunals are designed to provide full and fair trials while protecting U.S. national security during wartime. Human rights groups and lawyers say they are flawed.

Khadr is charged with conspiring to commit war crimes and with murdering U.S. Army Sgt. 1st Class Christopher Speer with a grenade during a firefight at a suspected al Qaeda compound in Afghanistan in 2002.

Khadr was 15 at the time. His lawyers said trying him before a military tribunal for crimes alleged to have been committed as a juvenile is a violation of international law.

Khadr now sports a short black beard and no longer looks like a child. He is being tried as an adult and would face life in prison if convicted.

Four Guantanamo defendants are scheduled for pretrial hearings this week before the tribunals President George W. Bush created after the September 11 attacks to try foreigners suspected of terrorism. The Supreme Court heard a challenge to their legitimacy last month and is expected to rule by July.

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