A British court martial of New Zealander Flight Lieutenant Malcolm Kendall-Smith will begin on Thursday (local time), when he will become the first British officer to face criminal charges for challenging the legality of the Iraq war.
But the Royal Air Force (RAF) doctor - who is alleged to have refused to return to Iraq because of his belief that the invasion of the Middle Eastern country was illegal - and his New Zealand-educated Queen's Counsel, Philip Sapsford, are expected to take the fight to the heart of Britain's Government.
Mr Sapsford said a key issue in the case will be whether Britain formally declared war on Iraq, and whether the subsequent actions of British soldiers were outside the legal confines of an act of war.
Flt Lt Kendall-Smith has already served in Afghanistan and on two tours of duty in Iraq but has refused to travel to the troubled Middle Eastern country for a third time, because he believes the British Government has no legal authority for the war it is waging there.
He refused to return to Basra - where two contingents of New Zealand engineers served - after British Attorney-General Lord Peter Goldsmith claimed that coalition forces were administering Iraq without lawful authority.
Mr Sapsford, who grew up in Christchurch and was educated there before becoming an international expert on human rights law, drew a parallel with the Nuremberg war crime trials at which judges said Nazi defendants should have refused orders which were illegal.
But Timothy Garden, a former assistant chief of the British Defence Staff, told The Australian newspaper he believed it would be extremely difficult to convince a British court that the current military activities by US-led forces in Iraq were illegal.
Flt Lt Kendall-Smith is expected to argue that the court must reach its own conclusion as to whether international law was breached by the Iraq invasion, which began without authorisation by any UN Security Council resolution.
The leader of his up to five-member legal team, lawyer Justin Hugheston-Roberts, said the case was "possibly the biggest case to come before any British court in living memory", as he believed the court could potentially find that the war in Iraq was illegal.
His client had not declared himself a conscientious objector to all wars, arguing instead that this particular conflict was illegal.
Gerry Simpson, a specialist in international law at the London School of Economics, told The Australian: "To defend yourself on that basis, you would have to convince the court that the war itself was illegal so you should be excused from service.
"Courts in the UK are reluctant to interfere with the (Government's) prerogative to go to war but it is not inconceivable that the court might examine whether the war is, in fact, in breach of international law."
Flt Lt Kendall-Smith holds dual New Zealand and British citizenship, and is five years into a six-year contract as a doctor with the RAF. He was born in Brisbane and attended primary school and university in Dunedin, where his parents Ian and Margaret Kendall-Smith still live.
Their son graduated from Otago's school of medicine in 1991 and then worked for a year at Dunedin Hospital before moving to Australia for more hospital experience.
This is cache, read story here