He didn't. The use of drones to take people out has been going on for years, for better or worse, and to this point nobody has pitched much of a fit about it.
Obama conducted a manned assault inside Pakistan without their knowledge or consent and didn't consult with Congress beforehand either, FFS, and I do not recall these same assholes bitching then.
This is a clear win for Trump and they don't like it. It is that simple, so they have to find something to criticize to try to blunt that win for him.
And **** them. His call. His W.
If there are consequences those will be his also, but for now he made the call, got it done and these whiny ***** can just STFU and go chase some other nonsense.