Read the second paragraph of that section. And sorry, Hague convention not Geneva. Either way, only special circumstances aka special operations from my understanding, which is more like international policing than warfare.
I don't know what the effect would be of USA participation in a NATO action using expanding small arms ammunition.
Seems kinda odd to me anyway, though I suppose limiting the damage a combatant receives while fighting isn’t a bad thing. Coming up with a stance makes you have to mentally address the concept of good vs bad guys, and I suppose I don’t see enemy fighters as bad people, just people fighting for differing ideals. That makes me tend to agree with rules that limit fatalities and excessive injury.