In the 1980s, in Germany where I was stationed, terrorists were tried in abstentia, and posters were published with their faces and names.
They were generally shot on sight, by the polizei, wherever and whenever encountered. After a certain number of them were X’d off the posters, another poster was printed.
I don't remember the polizei executing any of them in, for example Italy.But if Italy had given consent to the polizei to operate there, than no problem.
A) We are the United States of America, and are a constitutional republic. We are not a democracy, and we are not Germany or Italy or etc.
B) There is a body of law dealing with outlawry and terms on wanted posters vis-a-vis rewards for capture. In this I don't think there a legal construct that comprises a way of making a list of adjudicated and declared terrorist, who can be killed on sight (i.e. wanted dead or alive). This differs from terrorists or criminals being killed in an armed struggle or firefight, or confrontation resisting arrest.
C) Wanted and reward posters are historical in the western territories, just as now. But not wanted dead or alive in the construct of legal to assassinate on sight.
Some of the homeland security laws we have approved in the US post-9/11 are way over the line of historical personal freedom. It was expedient, but how will they ever be rescinded? How will posse comitatus and due process protect the citizenry from a federal government police force? The department of homeland security has purchased 1.4+ billion rounds of handgun ammo. (...likely purchased for maintaining order and mob suppression in the case of general civil upheaval?)
We aren't Germany. OK.
But the way we are headed, someday we may not be the good ole' USofA anymore.