Recent history demonstrates that if President Barack Obama, arguably the most powerful person on planet Earth, wants to prioritize almost anything – from pardoning 46 convicted drug felons to bombing a foreign countrywithout the consent of Congress – little can stand in his way. Why, then, is Shaker Aamer not home in London with his wife and four children?

Aamer is the last British resident to be detained without trial in Guantánamo Bay and he has never been charged with a single offense. In 2007, he was cleared for release by the Bush Administration; in 2009, six US intelligence agencies unanimously agreed that Shaker should be released. In January 2015, British Prime Minster David Cameron personally raised Shaker's plight with President Obama, who promised that he would "prioritize" the case.