(CNN) -- A judge has ordered that the beard of Maj. Nidal Hasan, the Army psychiatrist accused of fatally shooting 13 people at Fort Hood, be forcibly shaved ahead of his upcoming military trial, base spokesman Tyler Broadway said Thursday.
Col. Gregory Gross issued the order, which will likely trigger an appeal that would further delay a case that has dragged on since the 2009 mass shooting.
Hasan's attorney had filed an appeal when Gross threatened to order the shaving, but the appeals court said it wouldn't issue a decision until the shaving was actually ordered. Thursday's order by Gross opens the door for that appeal.
The last time he was in court, Hasan told the judge, "Your honor, in the name of almighty Allah, I am a Muslim. I believe that my religion requires me to wear a beard."
His defense team argued Hasan should be able to keep his beard under the Religious Freedom Restoration Act, contending that shaving it would leave him in a "perilous religious state," according to a news release from Fort Hood.
The defense contends Hasan's faith is genuine and has gotten stronger in the past year.
But government prosecutors argued he should have to shave his beard, saying having it long would make it harder for witnesses to identify him as the shooter in court.
They also said that Hasan, by keeping his beard long, is trying to associate himself with radical Islamic fighters known as mujahedeen, the Fort Hood press release said.
In his ruling, Gross determined that Hasan cannot keep the beard because it violates Army regulations. Even as he awaits trial for murder, Hasan is still an officer in the U.S. Army and subject to regulations.
Hasan's court-martial had been scheduled to start last month at Fort Hood, in Killeen, Texas, where he is accused of wounding 32 in addition to killing 13 people.
No further hearings are scheduled in his military trial, according to the Army base.
His lawyers can now go to the Army Court of Criminal Appeals, administered by the Judge Advocate General's Corps.
The next step would be the U.S. Court of Appeals for the Armed Forces, an independent tribunal with worldwide jurisdiction over active-duty members of the U.S. armed forces and others subject to the Uniform Code of Military Justice.
The District of Columbia-based court is made up of five civilian judges appointed for 15-year terms by the president. Decisions of the court are subject to direct appeal to the U.S. Supreme Court.
The full appeals process could delay Hasan's criminal trial for months if not years.
CNN's Bill Mears contributed to this report.