The lawyer defending Bradley Manning against charges that he "aided the enemy" by disclosing state secrets to the whistleblower website WikiLeaks, is arguing that US soldiers are being treated more harshly in application of the law than terrorists.

David Coombs, the civilian lawyer who has been representing the soldier for the past two years after he was arrested in Iraq on suspicion of being the WikiLeaks source, will be pressing his case in a military court next week. In a motion that he has lodged with the court as part of the lead up to a full court martial, he warns that unless the "aiding the enemy" charge is clarified it would leave Manning in a more onerous legal position than terrorists facing exactly the same count.

"It defies all logic to think that a terrorist would fare better in an American court for aiding the enemy than a US soldier would," Coombs writes in the motion.

Aiding the enemy is the most serious of the 22 counts that Manning is facing. In the rank of military charges, it is rated very close to treason and technically carries the death penalty, though the prosecution in this case have indicated that they will not push for that.

The charge alleges that between November 2009 and 27 May 2010, when Manning was arrested at a military base outside Baghdad, he "knowingly gave intelligence to the enemy through indirect means". In court deliberations, it has been further clarified that the charge refers to the transmitting of "classified documents to the enemy through the WikiLeaks website".

The US government has added in later legal debate that the "enemy" to which it is referring is al-Qaida and al-Qaida in the Arabian Peninsula, as well as a terrorist group whose identity has not been made public.

The allegations relate to the passing of hundreds of thousands of US state secrets, including embassy cables from around the world and war logs from Iraq and Afghanistan, that caused a worldwide sensation when they were published by WikiLeaks via several international news organisations led by the Guardian.

Next week the soldier and his defence team will be back in military court in Fort Meade, Maryland, in the latest of a succession of pre-trial hearings to hammer out the terms of the eventual court martial. Previous engagements have led to sparky interactions between Coombs and the army prosecutors seeking to condemn Manning possibly to spending the rest of his life in military custody.

The most significant discussion at next week's proceedings will revolve around the precise legal definition of what "aiding the enemy" means – specifically its allegation that Manning "knowingly gave intelligence to the enemy". The judge presiding over Manning's trial, Colonel Denise Lind, has ruled that the soldier must have had "actual knowlege" that he was giving intelligence to enemy for the charge to be proven.

Coombs will next week attempt to gain further clarification that would raise the legal bar much higher. In his motion he argues that it is a truism in the age of the internet, any posted material is potentially accessible to anybody.

To accuse Manning of having aided the enemy by transmitting intelligence to WikiLeaks that could then be accessed by al-Qaida would remove any sense of him "knowingly" doing so. He writes that this would "render the 'actual knowledge' element utterly toothless in all internet-intelligence

cases."

Coombs highlights an apparent absurdity in the way the law is being applied. In cases where terrorist suspects are brought before military commissions, such as those at Guantanamo, and accused of the very same charge as Manning, the military prosecutors have to prove that the defendant "knowingly and intentionally" aided the enemy. Yet in the case of a US soldier, intentionality is not mentioned.

The defence calls this a "very troublesome absurdity". Coombs states: "For the exact same conduct, a terrorist would benefit from a friendlier mens rea [guilty mind] than a soldier would. Congress could not have intended to give terrorists a more protective mens rea than it gave to soldiers."

If the defence motion is successful next week, Manning would be held to the same standard as terrorists. In other words, the government would have to prove beyond reasonable doubt that he had transmitted state secrets through WikiLeaks knowing and crucially intending that they would be helpful to al-Qaida and other enemies of the US.

The trial is scheduled for September, but may be pushed back as a result of lengthy legal wrangling and the slow pace at which the prosecution has been disclosing vital information to the defence.