I am fairly certain, that's illegal under the Posse Comitatus Act. Calling criminals "terrorists" doesn't change the fact that going after them for breaking US laws, constitutes "domestic law enforcement"...which is explicitly what the law prevents the military from engaging in, since there are already domestic law enforcement agencies for that.
This also doesn't even touch on the basic Constitutional right to due process that launching a drone strike would be violating. As far as how the law is supposed to work in the United States, none of this would qualify as "legal", no matter how you tried to justify it.
