The court martial of an RAF officer who refuses to serve in Iraq, because he believes the war is illegal, may have a global impact, his solicitor says.
Flt Lt Dr Malcolm Kendall-Smith is based at RAF Kinloss in Scotland
Flt Lt Dr Malcolm Kendall-Smith, 37, faces five counts of "refusing to obey a lawful command". He has previously served two tours of duty in Iraq.
A pre-trial hearing, before a judge advocate, is due to begin on Wednesday.
The Ministry of Defence said it was inappropriate for it to comment on the outcome of the trial.
Flt Lt Dr Kendall-Smith's lawyer, Justin Hugheston-Roberts, told BBC News that if his client was acquitted he would see it as a justification for his actions in not going to Iraq, but the "knock-on effect could be devastating across the world".
The medic had refused to return to Iraq "because he looks at his duty as a commissioned officer to examine and consider every single order that is given to him".
"He is an extremely astute and bright young man who has considered the requirements of what he is being asked to do and takes the view that, at this stage, those requirements make the order that he is being asked to carry out unlawful."
The officer was interviewed by the Special Investigations Branch (SIB) of the Royal Air Force Police in June 2005 and suspended on full pay.
He was served with court martial papers on 5 October 2005.
He faces five charges - four of which relate to preparations for the deployment and the fifth for refusing to go.
On Wednesday, a pre-trial hearing - lasting around five days - will begin hearing legal arguments, ahead of a court martial.
The purpose of the hearing was to "identify, clarify and rule upon" specific questions of law that both the prosecution and defence would be putting to the court, said Mr Hugheston-Roberts.
The judge's ruling on those questions of law would be binding on the court martial, he continued.
"We will be asking the court to consider whether or not his actions justify defence to a criminal charge."
While the court was having to rule on Flt Lt Kendall-Smith's actions, it was not there to rule on the legality of the war.
"It is a very, very fine line that the court is going to have to walk," he said.
A spokesman for the Ministry of Defence said it was taking this action against the individual because of his failure to follow "lawful command".
This was based on the advice given by the attorney general to the prime minister that the war was lawful, he added.