FORT LEWIS, Wash. —  An Army lieutenant who called the Iraq war illegal and refused to deploy cannot base his court-martial defense on the war's legality, a military judge has ruled.

Lawyers for 1st Lt. Ehren Watada planned to argue at the Feb. 5 trial that the war was illegal because it violated Army regulations that wars must be waged in accordance with the United Nations charter.

But in a ruling released Tuesday, Lt. Col. John Head said "whether the war is lawful" is a political question that could not be judged in a military court.

Watada, a 28-year-old Hawaiian native, is charged with missing troop movement last year. He is also accused of conduct unbecoming an officer for statements he made to journalists and at a veterans convention. He faces up to six years in prison.

Head also rejected lawyers' claims that Watada's First Amendment rights shielded him from charges stemming from his criticism of the war. Head said there are limits to the free-speech rights of military personnel.

"We have been stripped of every defense," said Eric A. Seitz, Watada's lawyer. "This is a disciplinary system, not a justice system. Otherwise, we would have been entitled to defend ourselves."

Army officials said in a statement they had full confidence in the military-justice system to ensure that Watada gets a fair trial.

Watada refused to go to Iraq last June with his unit, the 3rd Brigade, 2nd Infantry Division, after conducting research and deciding the war was illegal. He has said he would be willing to serve in Afghanistan or elsewhere.