Britain's Defense Secretary John Reid called for a review of the Geneva Conventions on Monday, and said international rules of war needed to be revamped to reflect the threats posed by global terrorism.
Reid said the potential for groups or countries to develop weapons of mass destruction raised new questions about the legalities of pre-emptive strikes. He also suggested that the Geneva Conventions - which date back to 1949 and govern the treatment of prisoners of war - may need to be revised.
"The laws of the 20th century placed constraints on us all which enhanced peace and protected liberty," Reid told an audience at the Royal United Services Institute, a security and defense think-tank in London. "We must ask ourselves whether, as the new century begins, they will do the same."
Reid did not specify any suggested changes to the Geneva Conventions or to the international rules of war - procedures based on the UN Charter, the Hague Convention and the Geneva Conventions that bind consenting nations.
Britain has been the strongest ally of the United States in its so-called war on terror, supplying thousands of troops in Afghanistan and Iraq.
Prime Minister Tony Blair has also defended the reasoning behind the US detention camp at Guantanamo Bay in Cuba where about 500 men accused of links to Afghanistan's Taliban or the al-Qaida terror network continue to be held - some for four years without charge. The men are classified as "enemy combatants," a classification with fewer legal protections than POWs under the Geneva Conventions.
"The legal constraints upon us have to be set against an enemy that adheres to no constraints whatsoever, but an enemy so swift to insist that we do in every particular, and that makes life very difficult for the forces of democracy."