War, in all its forms, is tragic. International law was created to establish some basis of rules to be respected – including war – and states have signed such a contract. The actions of states in this increasingly globalized world are difficult to control. The source of international law operates through the hands of the United Nations. Law enforcement occurs through reciprocity, collective action, and the implementation of international norms (Goldstein, p. 254). The war has in fact been given a justification, although it is questionable whether the basis of the idea is correct or not. Wars can be just under certain conditions. Just war doctrine was written to define a justification for wars. Ultimately, the legality of wars is established by the United Nations Charter. The just war doctrine divides the laws regarding war into two parts. The first is when war is permissible (jus ad bellum), the second is how a war is fought (jus in bello). A just war is separate from the principle of an aggressive war; just wars are legal, while wars of aggression are illegal (Goldstein, p.263). Aggression refers to the use of force by one state against the territory or sovereignty of another state. According to just war theory, although a war of aggression is illegal, a war fought in response to aggression is legal. This concept is the only permissible use of military force as stated in the just war doctrine. Just war theory develops around the concept of aggression. For a situation to constitute assault, the threat or use of force must be clearly visible. Since responding to aggression is the only permitted use of military force, it is not legal to attempt to change another state's government or its ideals. The UN Charter emphasizes that war is not… a means of paper… it is created automatically when uttered by the state that inhibits the threat. If no action were taken because states chose to stick to just war doctrine and disaster struck, the effects would ultimately be extremely harmful. Just war principles are useful and practical for today's world. However, as globalization increases and continues to impact the affairs of states, the principle may begin to lose its effectiveness. If states continue to do their best to meet international standards and set a standard for other states, there may be a possibility that all states will begin to do so: anything is theoretically possible. The expertise of just war doctrine has proven useful in keeping states safe and protecting their sovereignty. Just war theory is currently proving beneficial, although due to globalization it may become harmful.