M. Cain
Obviously, you are ignorant of the terms "illegal" and "war" - and I don't mean that as an ad hominem attack, "ignorant" in the sense of "not knowing" the definition. Such statements are Hollywood sound-bite platitudes without substance.
Legal systems require a (i) closed group, (ii) with common standards of conduct, (iii) that are agreed (or adopted) by everyone in the group, and (iv) the violation of which can be adjudicated and punished by a government that is separate from and controlling over the group.
By definition, two sovereign (catch that key word, there) countries are open groups, without common, agreed standards, with no supreme executive above them.
"War" by sovereign states is contrary to almost all terms of "legal."