So would the terrorist fear the mercenary holding a letter of Marque.
A letter in one hand and an automatic in the other. I met a guy who was ready to send his company in if the president decided to take this Constitutional path. Talk about a professional outfit. Osama and his little buddies would have been either dust or back in the US already. No doubt. It is also great propadanda value: no matter where you are, if you attack us we will find you. You won't know where or what the people who get you will look like. So look over your shoulder for the rest of your life, because a bounty hunter will likely be there to smoke your ass.
I'll bet.
Terrorists fear bombs, lots and lots of bombs.
Especially the kind that suck the air out their lungs and singe them irreparably so that they literally asphyxiate over several hours.