The issue with Anwar al Awlaki is not whether he was a citizen, or
even where he was. If we examine the legal history of the right of
due process, we find that it was not confined to citizens (or
"subjects" in the English context), or to the soil of the nation.
However, it was confined to those over whom personal jurisdiction is
established, as by holding one in custody. That means it excepts,
until they are made prisoners:
1. Foreign military personnel engaged in hostilities against us or
our allies.
2. Pirates, engaged in warlike acts against assets of nations other
than their own.
3. Traitors, U.S. citizens engaged in warlike acts against assets of
their own nation.
4. Violent felons, while actively engaged in crime.
It is that personal jurisdiction and custody that defines the
boundary between whether it is permissible to apply deadly force
without due process, or whether it is not. Citizenship and location
are irrelevant, except as to whether one is a traitor or a pirate.
Presuming the premise that Anwar al Awlaki was actively engaged in
hostilities (warlike acts) against the U.S., as a U.S. citizen, that
makes his activity treason. If he were not a U.S. citizen, and since
he was a nonstate actor, it would be piracy.
But he was not in custody, and it is a well-established principle of
law that while we should always try, if it can be done safely, to
secure custody of an offender, when it cannot the offender stands as
an "outlaw" — someone outside the protections of law.
The same principles apply to a self-defense situation: While the
offender is threatening injury or death one may kill him. but once
he surrenders one may not.
So the only questions are, (1) whether he was engaged in warlike
acts against the U.S. or its allies, and (2) whether it was safe to
capture him. If the answers were yes and no, respectively, then it
was permissible to kill him. And, yes, the president, and other
officials, do have the power to make that determination, subject to
review. If after a review it is found the determinations were
incorrect, then the officials may be held liable.