The man was very Publicly, and openly at war with his own country. He was a traitor, and he chose his Fate.
The irony of this is the Framers went out of their way to make treason difficult to prove, as it was so often misused as a political weapon by the regimes of their time.
Article III, Section 3 US Constitution:
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.
The authors were concerned about the definition of treason. They thought that it was used too broadly to define any dissenting opinions. Their new country would be much stricter about what treason was, and how one would be accused and convicted of it.
Treason, then, is defined only as going to war against the USA, or aiding the enemies of the USA.
To be convicted, the accused must confess to treason, or be accused by two direct witnesses of the treason.
Notes on the U.S. Constitution - The U.S. Constitution Online - USConstitution.net
Article III, Section 3 clearly states that one must be convicted of treason, in court, per due process. One must either confess in
a public proceeding or be accused by two witnesses.
Allegations of treason do not therefore mitigate, suspend, or otherwise do away with the defendant’s right to do process – as some have incorrectly argued.
ItÂ’s sad and troubling that Americans today are ignorant of this Constitutional stipulation and advocate that by committing acts of treason, one forfeits his Constitutional rights.
Lastly, no one is arguing that Anwar al-AwlakiÂ’s actions do not meet the standards of treason, or that there isnÂ’t sufficient evidence for indictment and trial, the argument is simply to adhere the Constitutional requirements as to addressing the issue of treason.