[Meta] Kill Orders and Legality

So every now and then the topic of Kill Orders in various fics comes up and its always bugged me slightly how the fanon is basically an 'outlaw' style system where anyone anywhen anyway can kill someone with a Kill Order and be rewarded for it, even if they walk up behind the person in a coffee shop and put a bullet in the back of their head.

Now logically I approve of it for high degree threats but I just don't see how such an order could be legal in the United States, even one that has changed due to parahumans.

Declaring a person extremely dangerous and authorising lethal force if necessary by police officers? Yeah that's legal and happens IRL, but out and out putting a wanted dead or alive bounty on someone without a trial? No, sorry, can't see it. It's very very unconstitutional and without a Contessa interrupt I don't see it happening.

Now trying an extreme threat in absentia (Jack Slash, Niborg, etc) and handing down a death sentence and then issuing bounty, that's legal if shady as hell.

It could even be used to explain why Kill Orders were rarely seen in canon and not even Bakuda got one when she was on her bombing spree. Oh if she has died resisting arrest no-one would have raised a fuss, but it was still an arrest not a targeted assassination.

So what say you? Over used in fanon and something that would likely be issued rarely when someone is tried in absentia or a butterfly in the Worm universe timeline?