Apparently the USA considers this legally acceptable "Proportionality" according to the wording of the Geneva Conventions, and therefore not a war crime. It is a highly bullshit interpretation according to many lawyers, but they have not been dragged to the Hague over it yet and probably never will be for many reasons. For one because nobody ever takes a swing at the USA in the ICC over anything due to political fallout, 2 because most other countriea are guilty of similar crimes and 3 because it is just too gosh darned convenient for the world power nations to be able to bomb apartments to hopefully kill one guy who they're pretty sure is a terrorist to keep their shipping lanes open for business. I actually wonder if there is any real legal line of Proportionality that could be crossed, one terrorist in a fully-booked children's hospital: still OK?

https://casebook.icrc.org/a_to_z/glossary/proportionality

Personally I think any extrajudicial executions are unacceptable. If the guy is a terrorist then arrest, try and convict him. If that's "too hard" then the answer is not to send a drone strike at an apartment building, or a wedding, or a hospital.