The 'Law of War' clearly defines how attacks on civilians can constitute a ware crime:

Article 51(5)(b) forbids any attack ‘which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated’. Such attacks will be classified as a war crime.

https://legalanswers.sl.nsw.gov.au/hot-topics-80-internation...

Given the fact USA drone strikes have bombed at least a handful weddings, under that definition those actions go very close to being a war crimes.