No, if I kidnap someone it's kidnapping. If the police based on probable cause receive and execute a warrant for someone's arrest, it's an arrest. This is how the state monopoly on violence works.
https://en.wikipedia.org/wiki/Extrajudicial_killing#United_S...
'Extrajudicial killing' is just an apologetic euphemism. An indirect term, since murder is usually considered to be a bad thing.