Read this entire article. It is lengthy but well worth it.
The links connecting Anwar al-Awlaki to anti-American terrorism were entirely suppositious, forged through unsubstantiated official assertion. He was, at most, a clerical propagandist who never exercised command authority. For that matter, no evidence has been presented that he ever had an operational role in a military force of any kind.
Awlaki — an American-born cleric who was once courted by the Pentagon — was accused of expressing support for armed attacks against U.S. military personnel and government interests. It is not terrorism to employ lethal violence against an invading and occupying army, nor is it a crime to express support for armed self-defense — or even to call for the violent overthrow of the U.S. government (or do I repeat myself).
The administration asserted – without providing evidence – that Awlaki had an “operational” role in planning terrorist attacks against U.S. citizens. If evidence supporting that charge existed, the administration had the unconditional constitutional duty to indict Awlaki and put him on trial.
Intelligence officials knew Awlaki’s location. The government of Yemen, which is headed by a pliant thug named Ali Abdullah Saleh, is a wholly owned subsidiary of Washington and would have eagerly cooperated in an effort to track down and extradite Awlaki. But this would not have validated the claim – made by the Bush administration, and embraced by its successor – that the President of the United States isn’t bound by the Constitution, but rather is the Living Constitution.