Technology has made stopping terrorist attacks harder, and it is legal to kill militants overseas if they pose an immediate or otherwise unstoppable threat, Britain's top law officer said Wednesday.
Attorney General Jeremy Wright used a speech at a London think tank to give a rare public account of the legal basis for the controversial policy.
A Royal Air Force drone strike in Syria killed three Islamic State group fighters in 2015, including two Britons. It was the first such strike acknowledged by the British government, and triggered calls for officials to disclose the legal advice justifying it.
In advance excerpts from the speech, Wright argued that "technology has made it easier for terrorists to carry out attacks."
"It is used to evade law enforcement, to conceal those who would do us harm, and to inspire attacks around the world that previously would have taken months of planning," Wright said.
"The situation we face today does not always allow for the possibility of using criminal law enforcement measures to stop attacks," he said.
Wright said Britain "will only act in self-defense, where it is consistent with international law."
But he said legal standards must evolve when it comes to judging when a threshold has been crossed.
Wright said the issues to be considered include how certain it is that an attack will come, how soon it could be and on what scale, and whether anything could credibly be done to prevent it.
"The world is changing fast, and we must be sure the law is keeping up," he said.
Shami Chakrabarti, legal affairs spokeswoman for the opposition Labour Party, said the law cannot be updated or changed by a speech and that it's vital "U.K military action complies with both domestic and international law."