LONDON — British troops are not protected by human rights laws on the battlefield, the Supreme Court ruled Wednesday, after the government argued that such protection could hamper military decision-making.

Six of the nine justices in London overturned rulings by the High Court and Court of Appeal in the case of a British soldier who died in Iraq in 2003 of a cardiac arrest after suffering the effects of extreme heat.

A 2006 inquest into Private Jason Smith's death blamed a "serious failure" by the army to recognise how the heat was affecting the 32-year-old, and his family launched a legal action that became a test case of soldiers' rights.

While the Ministry of Defence conceded that soldiers on British military bases or hospitals were protected by the Human Rights Act, their lawyers argued it was impractical to extend such protection to battlefield situations.

"The imposition of some form of legal duty of care would create a major and disproportionate risk that military decision-making would be made more cumbersome and would be skewed in the light of it," their lawyer James Eadie had argued at the Supreme Court in March.

Although the ministry lost its argument at the High Court and then the Court of Appeal, those rulings were overturned at the Supreme Court on Wednesday.

Justice Lord Alan Rodger said: "While steps can be taken, by training and by providing suitable armour, to give our troops some measure of protection against these hostile attacks, that protection can never be complete.

"Deaths and injuries are inevitable."

He added: "To suggest that these deaths and injuries can always, or even usually be seen as the result of some failure to protect the soldiers... is to depreciate the bravery of the men and women who face these dangers."

Jocelyn Cockburn, the lawyer for Smith's mother Catherine, said the decision was "shocking", adding: "It is artificial to assert that rights can be protected on base but not off base."

However, Defence Secretary Liam Fox said "common sense has prevailed", adding: "It would have been absurd to try to apply the same legal considerations on the battlefield that exist in non-combat situations."

Britain has withdrawn from Iraq but about 9,500 British troops remain in Afghanistan, most of them battling Taliban insurgents. A total of 309 have died since 2001.