Reply #21: That's a question of which set of laws you're using [View All]

[Euromutt]

The rules that govern the conduct of combatants (like the Geneva Conventions) are known collectively as ius in bello, "law in war." International law regarding the legitimacy of the war as a whole, rather than the conduct of those fighting in it, is known as ius ad bellum, "law towards war." Your question falls under the latter.

Unfortunately, ius ad bellum has historically been honored more in the breach than in the observance, and it's been in some measure of flux since the end of the Cold War, with the advent of "humanitarian interventions" (i.e. military action by a country to stop what it considers to be illegitimate behavior by another government, even though the intervening party has not been directly affected). The best chance thus far at establishing precedent was scuppered when Slobodan Milosevic died (in effect, unintentionally killed himself) before the ICTY's court delivered a verdict.