Current international law does still matter, each time a state takes such action without consent other states object, they are simply not powerful enough to prevent it but this does prevent any norm being created by the aggressor.  If however international law does no longer matter then any war is legal, or rather at least not illegal. This potentially means going back to a situation where any state has a sovereign right to engage in conflict for almost anything it sees as an infringement of its sovereignty. The best we might hope for would be that states could agree that while war might be legal it has to be under the conditions of launching a just war under jus ad bellum. There are six requirements:  just cause – defence of oneself, allies, or innocents or punishment for wrongdoing  right intention – no ulterior motives beyond the stated cause  Proper authority and public declaration – must be open and done publically  Last resort – have expended all peaceful alternatives  Proportionality – must create more good than evil so that the action is worth the costs  Probability of success – there must be some likelihood of making a difference and concluding the conflict quickly. [1]  In most cases military action would not meet all of these requirements.  [1] Orend, Brian, "War", in Edward N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Fall 2008 Edition),   Also see the debatabase debate ‘ This House believes there can be such a thing as a just war ’