Brig Gen Hartmann was appointed to provide impartial legal advice
A military judge has barred a US general from the second war crimes trial at Guantanamo Bay.
The judge, Col Steve Henley, ruled that Air Force Brig Gen Thomas Hartmann, legal adviser to the tribunal, had compromised his objectivity.
Brig Gen Hartmann allegedly "pushed" for Afghan detainee Mohammed Jawad to be charged because of the "gripping" details of his case.
However, moves to dismiss the charges against Mr Jawad were rejected.
Col Henley ruled that the legal adviser's public statements aligning himself with prosecutors and defending the Pentagon's system for prosecuting terrorists suspects had compromised his objectivity.
Brig Gen Hartmann, who was appointed to supply impartial legal advice to the Pentagon appointee overseeing the proceedings, was also barred from the first Guantanamo Bay war crimes trial against Osama Bin Laden's former driver.
In the current trial, Mr Jawad is accused of throwing a grenade into a US military jeep at a bazaar in Kabul in December 2002. He is charged with attempted murder.
Former chief prosecutor, Air Force Col Morris Davis told the hearing: "The guy who threw the grenade was always at the top of the list."
It was also alleged that Brig Gen Hartmann was "abusive, bullying and unprofessional".
It is now expected that there could be further legal challenges concerning the legal adviser's role in other cases.
Lawyers for the five men accused of involvement in the 11 September attacks - including the alleged ringleader Khalid Sheikh Mohammed - are also challenging Brig Gen Hartmann's involvement in the preparation of charges.
Brig Gen Hartmann supervises the chief prosecutor at Guantanamo Bay, which is in Cuba, and has extensive powers over the tribunal system.