When Barack Obama first campaigned for the White House, he promised a return to constitutional law after the “war on terror” excesses of the Bush years. The leak this week of portions of his administration’s memo justifying the targeted killings of terrorist suspects, including US citizens, suggests Mr Obama has fallen well short of his original promise.

The memo’s legal reasoning differs little from George W. Bush’s grounds for torture, secret rendition and wiretapping of US citizens – all of which Mr Obama rightly criticised as breaching executive authority. Mr Bush was eventually forced to ban “enhanced interrogation techniques” and put wiretapping on to a legal footing. Mr Obama should move rapidly to do the same for drones.

The US is a nation of laws. No US president should have the exclusive power of life and death over civilians, whether they are US citizens or not. It is perfectly reasonable for the US to target al-Qaeda suspects who are beyond the reach of the law – this is legitimate self-defence. But that power must be subject to judicial and congressional oversight. Upwards of 150 – and possibly as many as 900 – civilians have been killed in US drone strikes, including four Americans. Yet in most cases the US government does not even acknowledge the strikes took place. On Wednesday, Mr Obama provided the full memo on drones policy to senior members of the Congress intelligence committees. But the document is more than two years old. And it is riddled with language that could permit targeted killings in many circumstances. It does not meet even the flimsiest rule of law test.