WASHINGTON — President Barack Obama steered the nation’s war machine into uncharted territory Friday when a U.S. drone attacked a convoy in Yemen and killed two American citizens who had become central figures in al-Qaida.

It was believed to be the first instance in which a U.S. citizen was tracked and executed based on secret intelligence and the president’s say-so. And it raised major questions about the limitations of presidential power.  http://www.airforcetimes.com/news/2011/09/ap-drone-strike-on-2-americans-raises-questions-093011/