In early February, a leaked white paper from the Obama Justice Department caused a small stir, because it laid out an expansive set of circumstances under which the president could order a citizen killed abroad. In September 2011, the US killed Al Qaeda propagandist Anwar al-Awlaki and Samir Khan, both US citizens, and a few weeks later a US drone strike in Yemen also killed Awlaki's 16-year-old son, Abdulrahman.
Early claims from US officials were that Abdulrahman was over 21 and a fighter for Al Qaeda at the time of his death, though those were walked back after relatives in America provided a birth certificate that showed he was born in Denver in 1995. It's not clear if Abdulrahman was specifically targeted or merely collateral damage in a strike that killed an adult and another teenager.
Meanwhile, the UK is stripping people it alleges of having joined militant groups of their citizenship, some of whom have gone on to be killed in US strikes. Stripping people of their citizenship, strips people of whatever protection they theoretically had as citizens under UK law.
An investigation by The Independent newspaper out today says that since 2002, when a law allowing dual nationals to be stripped of their citizenship for doing something "seriously prejudicial" to the UK was passed, 21 people have had their citizenship taken away. That pace has dramatically increased under the current government, with The Independent reporting that 16 of that total have had their citizenship taken away by the order of Home Secretary Theresa May since 2010.