ALEXANDRIA, Va. (AP) — Zacarias Moussaoui has a right to learn the government's theory of his alleged role as a conspirator with the Sept. 11 hijackers, a judge says.

U.S. District Judge Leonie Brinkema told the government Monday that unless it could justify treating the new prosecution theory as classified, it must share the information so that Moussaoui -- representing himself -- can prepare his case.

Moussaoui has argued the government now views him as a fifth pilot of an attacking plane rather than the 20th hijacker on Sept. 11. The acknowledged al-Qaida loyalist contends he was not part of the attack plan that day, as charged in an indictment.

The new government theory has not been publicly disclosed, so it was unclear whether prosecutors still believe Moussaoui was part of the Sept. 11 plot or a planned second wave of attacks. He was arrested before the attacks after employees at a flight school became suspicious of his conduct.

"To refuse to do so would undermine Mr. Moussaoui's ability to mount his ... defense," the judge said in a written order. Brinkema will review the transcript of a Jan. 30 hearing where the government disclosed the change, but hid it from Moussaoui. He was not permitted to attend the hearing because classified information was discussed.

Moussaoui received a heavily edited version of the hearing transcript. However, Moussaoui also received a version of a March 10 court opinion that included a reference to the change.

That prompted him to seek greater disclosure in a "Motion to Know How the United Satan is Lying to Murder Me By Legal Means." The government said it would seek the death penalty if Moussaoui is convicted.

Prosecutors have opposed Moussaoui's request, arguing the indictment provides Moussaoui with ample notice of the charges against him. Also, the government said, he is not entitled to classified information or a preview of the government's case.

Brinkema said the government's argument would be correct in most cases, but in this instance, prosecutors voluntarily disclosed their change in the January hearing to Moussaoui's court-appointed lawyers.

While Moussaoui refuses to speak with them, the judge said if prosecutors shared the theory with the defense team, they also have to disclose it -- in an unclassified form -- to the defendant so he can prepare his own case.