The fact Anwar Al-Awlaki was a citizen was more of a technicality, than it was of any consequence. His actions made him ripe for the picking, so to speak. If I did the same, I would expect the same, as would most Americans. I think even he did, which is why he tried to hide his whereabouts so carefully. Even he had enough sense to know being a United States citizen wouldn't shield him. There is a simple solution to all of this. If you want to be treated like an American citizen, then act like one, not it's enemy.
Stretching this into gun control doesn't make any sense. I can lose my gun rights as a Citizen by simply committing a felony, or less. And rightfully so. If I want to retain my gun rights I must behave and observe the laws of the land. Once lost it is a time consuming and costly legal procedure to reinstate them. In this country if you are convicted of misdemeanor domestic violence you will lose your gun rights. If you do what Anwar Al-Awlaki did you will lose your life. He played the same exact game Bin Laden did. His outcome was the same as well. Both plotted, and succeeded in killing innocent Americans. The fact one happened to be a citizen had no bearing, nor should it have.