What are the characteristics of international law?

International law is not imposed on states — there is no international legislature. The international legal system is decentralized and founded essentially on consensus. International law is made primarily in one of two ways: through the practice of states (customary international law) and through agreements entered into by states (treaties). Once international rules are established they have an imperative character and cannot be unilaterally modified at will by states. The absence of a strong enforcement machinery is highlighted by skeptics as a weakness of international law. There is no international police force, nor is there an international court with compulsory jurisdiction to which states are required to submit. That is not to say, however, that international law is not effective. Sanctions are available which may be employed and which may affect a state's conduct. If international law is violated there are a number of self-help measures which the victim state may adopt, for example, a treaty may be suspended or terminated, or the assets of an offending state may be frozen. The United Nations Security Council may authorize economic sanctions. Force may be used in defined circumstances.

Public opinion can also be an effective sanction. States want to be seen to be adhering to international law: why otherwise do they go to considerable efforts to justify their particular position in international law?

There is an international court to which states can refer their disputes for settlement. States, however, must agree to submit to the court; there is no legal compulsion on them to do so.

The international legal system is different from municipal law. The principal participants of the international legal system states are all treated as equally sovereign. The international community is composed not of a homogeneous grouping of states, but rather a heterogeneous group of some 185 states, which differ politically, economically, culturally and ideologically.

The international legal system is a young, immature system which is constantly evolving and developing. It is not simply lawyers' law. Politics play an influential role. Consequently, the study of international law facilitates a greater comprehension of, and gives an insight into, the functioning of the international community.

Function of international law

Law is a closed system of rationality, a thought-world unto itself. Law is a systematic actualizing of a given society's values. Law is an expression of the totality of a society's existence. Law is inevitably connected with our ideas about the ultimate things – our ultimate ideas about the natural world, and our ultimate ideas about humanity's relationship to the supernatural and the spiritual.

This is the wonder of the law-phenomenon. Law achieves this wonderful feat of dialectical integration in an amazingly efficient way, day after day, year in, year out, like some marvelously engineered machine.

But first we have to try to answer the question: how does law achieve all this? What is the secret of its amazing society-making capacity? To answer this question we have to move the focus in one step closer and say how law works. It is another extraordinary fact that law students leave law school with very little idea of how law works. They have learned the procedures, the tricks of the trade, some legal principles, perhaps, the names of famous cases, where to look to find the law. But, normally, they have not even the most rudimentary idea of how law works, mechanically, so to speak, of what is under the hood of the legal motor car.

What law does is to allow a society to choose its future. Law is made in the past, to be applied in the present, in order to make society take a particular form in the future. Law carries a society's idea of its own future from the past into the future. Law carries society's structures and systems from the past into the future. Law makes possible society's possible futures.

For example, a law on environmental management. Such a law conditions the behavior of those who may be planning a new industrial project. It conditions the behavior of those who want to react to that proposal. It conditions the behavior of those who have power to permit, prohibit, or modify the proposal. When the environmental management law is applied in a particular situation, the outcome is produced by an intersecting of the behavior of all the relevant people in such a way that the net outcome is within the range of possibilities which have been defined by the law as serving the common interest of society as a whole.

That is the way law works. It enacts in a particular form the common interest of society as a whole. It then disaggregates that common interest by relating it to the actual detailed behavior of particular society members. And the result is that, in taking their individual self-interested decisions, individual society members, if they act in conformity with the law, also and inevitably serve the common interest of society.