There's a debate raging within and among the Obama White House, the Justice Department, the CIA and the Pentagon over how best to kill an American citizen without criminal charges ever being filed against him. The American citizen is not named, but is said to be a "terrorist facilitator" hiding out in a remote area of Pakistan.
According to the policy changes made by Obama last year, only the US military can kill American citizens in drone strikes. Pakistan, however, doesn't allow US military operations on its soil, having kicked it out a few years ago. They do allow the CIA to conduct drone strikes on its territory, but under Obama's new rule, the CIA can't kill American citizens—at least not legally. As is usual, however, we only have the word of anonymous administration officials quoted in the news media that the person in question, who has not been named, is actually who they say he is, since they have no interest in taking their case against this person to a court where it can be properly adjudicated. In other words, once they make their decision, it'll be a repeat of the killing of Anwar al Awlaki in Yemen in 2011.
So much for the US Constitution.