International law deals with relationships that reach beyond the borders of any one country. International laws and institutions are used in situations such as:
- dealing with crimes committed across or beyond borders, for instance a murder on board a ship in international waters
- regulating international travel by sea or air, or across land borders
- deciding on the rights different countries have to tax income from international transactions
- dealing with allegations that a parent has breached custody rights by abducting a child from one country to another
- regulating contracts for the sale of goods and services between countries, such as the sale of New Zealand dairy products to China
- dealing with pollution from a foreign source, such as the impact on a coast of an oil spill from a foreign-flagged vessel operating in international waters.
There are also many circumstances that arise from the very existence of almost 200 countries, and from the relations between them. Over centuries law has been developed to deal with these situations through practice (known as customary international law), agreements (known generically as treaties), general principles of law, court decisions and scholarly writing.
The functions of international law
The functions of many rules of international law are essentially the same as those of national law. They may:
- establish constitutions of international organisations, such as the Charter of the United Nations
- be equated to legislation (written law), such as the United Nations Convention on the Law of the Sea or The Hague Convention on the Civil Aspects of International Child Abduction
- determine boundaries between nations
- be bilateral contracts involving a mutual exchange of promises, such as contracts about air services between different states, of which New Zealand has about 40.
Areas covered by international law
The subject matter of international law is extensive and growing, as its emphasis moves from the coexistence of states to cooperation between them. Some parts of international law are so integrated into national law that they have become indistinguishable from it.
Among the many areas covered by international law are:
- regulating when armed force can be used by states, and setting the rules for armed conflicts
- disarmament and arms control
- aspects of statehood, including recognition of states, their territory and their diplomatic relations
- how states can acquire land and maritime areas
- international trade, finance and commerce
- international communications
- international spaces (sea, air, outer space, arctic areas, rivers and canals)
- the environment
- labour relations and human rights.