Story: International law

Page 1. What is international law?

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International law deals with relationships that go 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 international 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 in the sale of New Zealand dairy products to China
  • dealing with pollution from a foreign source, such as the impact on a coast by 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 across the world and from the relations between them. Over centuries law has been developed to deal with all of 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 the 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.

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.
How to cite this page:

K. J. Keith, 'International law - What is international law?', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/international-law/page-1 (accessed 23 September 2019)

Story by K. J. Keith, published 20 Jun 2012