Barack Obama is a former law professor who was awarded the Nobel Peace Prize. So it is ironic and disturbing that his administration is presiding over a prolonged campaign of assassination of terrorist suspects in Pakistan and Yemen, through attacks by unmanned missiles, known as drone strikes.

Over the weekend, a protest march led by the politician Imran Khan was prevented from entering the areas of Pakistan that have been heavily targeted. Pakistani protests against the drone strikes may evoke little sympathy in the US – given widespread exasperation over Pakistan’s failure to deal with Islamist militants that use the country as a base, and the fact that al-Qaeda and the Taliban remain a real threat.

Critics of the drone strikes are not confined to Pakistan, however. Independent investigations have raised disturbing questions that deserve to be answered.