The US government must prove that Bradley Manning knowingly helped Al-Qaeda by leaking secret documents to WikiLeaks in order to convict him of "aiding the enemy," a judge ruled Wednesday.
The ruling by Judge Denise Lind at a preliminary hearing raises the bar for convicting Manning -- who has admitted leaking the documents but denied aiding the enemy -- of the most serious charge he faces.
Lind said the prosecution in the military tribunal must prove "beyond a reasonable doubt" that Manning had "reason to believe such information could be used to the injury of the US," by an armed group like Al-Qaeda or another nation.
The 25-year-old US Army private admitted in February to leaking a trove of secret war logs and diplomatic cables to Julian Assange's WikiLeaks website and said he would plead guilty to 10 of the less serious charges against him, which could see him sentenced to 20 years in military custody.
Manning has denied aiding the enemy, which would carry a life sentence.
Lind also ruled that the government can call as a witness one of the commandos who took part in the 2011 raid that killed Osama bin Laden.
The Navy SEAL would testify on condition of anonymity that documents leaked to WikiLeaks were found in the Al-Qaeda leader's compound in Abbottabad, Pakistan.
The judge thus discarded a defense motion to "preclude evidence that Al-Qaeda or Al-Qaeda in the Arabian Peninsula allegedly received" the information in question.
The hearing, due to wrap up later Wednesday, was the first since a group pressing for more government transparency flouted a military ban by releasing a secretly-recorded audio clip of Manning's testimony.
The leak marked the first time since Manning was arrested in May 2010 that the world has heard his voice.
It was secretly taped on February 28 when Manning explained why he funneled a trove of US military and State Department documents to secrets-spilling WikiLeaks between November 2009 and May 2010.
"To say that the judge was unhappy about this violation of the rules of the court would be an understatement," a military spokeswoman told reporters covering the hearing.
As a result, mobile phones and recording devices, previously only banned inside the courtroom, are now outlawed in the press gallery as well, where the hearing is being broadcast.
"This media operation center is a privilege, not a requirement. Privileges can be taken away," the spokeswoman said.
Manning's trial is set to begin on June 3 at Fort Meade near Washington.