In a severe rebuff to the Bush administration's claim of inherent authority during the war on terror to hold enemy combatants or suspected terrorists indefinitely, the US Supreme Court has struck down key elements of administration policy.

The apex court said the executive branch does not have the authority to deprive accused members of al Qaeda or the Taliban of their liberty without giving them a day in court.

The court also said the president may order a US citizen detained as an 'enemy combatant' but rejected administration's expansive interpretation of that authority. It ruled that such detainees are entitled to contest government's case.

In another ruling, the court determined that each of the 595 alleged members of al Qaeda and the Taliban being held at the US base at Guantanamo Bay, Cuba, has the right to ask a US judge to set him free.

Justice Sandr Qa Day O'Connor wrote: "It is vital that our calculus not give short shrift to the values that this country holds dear or to the privilege that is American citizenship."

"It is during our most challenging and uncertain moments that our nation's commitment to the process is most severely tested, and it is in those times that we must preserve our commitment at home to the principles for which we fight abroad," he said.

"We have long since made clear that a state of war is not a blank cheque for the President when it comes to the rights of the Nation's citizens," he added.