This week’s capital charges against six 9/11 suspects are renewing fears the prisoners could be executed at Guantanamo Bay if found guilty. Pentagon regulations have long required death sentences to be carried out by lethal injection at Fort Leavenworth in Kansas. But two years ago, the military amended its rules to allow for “other locations.” Experts say a death sentence at Guantanamo would be difficult to challenge in U.S. court.