Since there is no common governing power that supervises all countries, despite the existence of international organizations such as United Nations, states find themselves unable to trust each other. Thus, they usually treat each other as possible opponent that could grab them anytime.
On the other hand, the modified structural realists believe that since there is anarchy in international relations, the weaker states have to look for means in order to protect its security and interest, as opposed to the powerful states, which tend to resist regulation or control of their movements.
Similar to the modified structural realists, neo-liberal institutionalists believe that adherence to international legal principles would help promote transparency in international dealings, reduce transaction costs in international trade, intensify strict monitoring and enforcement of contractual obligations, and eases imposition of penalties for violation thereof. Voluntary observance of the international legal principles would encourage more cooperation in the international arena that would somehow grant long-term benefits, especially in the financial aspects.
The hegemonic stability theor...
e theories point to only one thing: the creation and observance of international legal principles are supported by the quest for protection of self-interest by the international stakeholders. Clearly, an independent state would not want to impose upon itself a rule that would ultimately restrict its freedom, if it will not reap any benefit from it. It cannot be denied that this voluntary adhesion to certain legal principles is no longer governed or motivated by the spirit of altruism. States need to protect themselves. Nobody can do it better than themselves.
In the humanitarian aspect for example, every state must choose to create a standard that would protect its people against unwarranted human rights violations. This is especially true in terms of physical violence where no specific ideology or religion could divert or amend the standards for all human beings because of the basic knowledge that all humans are equal in feelings. If a state for example would think of exempting itself from the international standards of human rights, common sense dictates that it should prepare itself for possible retaliation in the most inhumane way since the state itself does not observe any standards for physical violation of its citizens.
A classic example on this one is the law on war. The killing of a war prisoner is generally prohibited. If the United States for example would kill an Iraqi soldier who was left by his troops during a fight and who was captivated by the American soldiers would be killed, Iraq would then have every reason to kill an American war prisoner because the United States in this case was the first one to violate the rights of such war prisoner. To create and obey this particular international legal principle is then more of a reciprocal benefit