What it is: A complicated collection of treaties, agreements of various kinds, customary codes of behaviour, United Nations resolutions and legal decisions concerning the relationships between the world's states, especially to do with human rights, commerce and war. Probably the best-known agreements - and the most often cited - are the Geneva Conventions. These international agreements (signed by almost every country) lay down basic rules for the treatment of war-wounded, prisoners of war, civilians, refugees and other victims of armed conflicts. Genocide and other 'crimes against humanity' are prohibited under international law. There are also agreements banning the production and use of 'bacteriological, biological and toxic weapons', 'excessively injurious' conventional weapons, chemical weapons, landmines and similar weapons. In 2005 the international legal status of nuclear weapons was still unclear.

What it means: The first Geneva Convention, brought about by the founder of the International Red Cross in 1864, began the on-going process of trying to codify and control the behaviour of states in war and armed conflicts. One problem has been the lack of means to enforce international law. The International Court of Justice was set up in 1946 to settle disputes between states, but the disputing states must agree to its adjudication and undertake to accept the judges' decision. An international military tribunal was set up at Nuremberg after the Second World War to try Nazi war crimes, with limited success. But it was not until the 1990s that international tribunals were again created, one to try the perpetrators of genocide in Rwanda, another to deal with war crimes committed in former Yugoslavia. In 1998 it was finally agreed to set up a single International Criminal Court (ICC), which opened for business in March 2003. The United Nations, since 1948, has also worked to codify and support international law. Yet increasingly bloody wars and armed conflicts broke out again and again throughout the last half of the 20th century. War is by nature destabilising. In the desperate attempt to win, survive and avenge, people quickly abandon civilised behaviour and rules. This is easy to do in 'the fog of war', which hides many actions from public view. Only after the conflict do some atrocities and injustices come to light. Some international laws are ignored by state governments, who continue manufacturing or stockpiling illegal weapons, refuse to accept the authority of the International Court of Justice or the existence of the ICC, treat prisoners of war unjustly, or go to war without the backing of the United Nations. (The UN charter outlaws the use of force except in self-defence or when authorised by the UN Security Council to deal with aggression or a 'threat to peace'.)

Think about it: Some people say that 'the laws of war belong to everyone. They are among the great achievements of civilisation'. Others would reply that making laws for war is a way of ensuring that war is an accepted feature of civilisation: it is war itself that should be made illegal. War and the activities it encourages are the most barbaric practices we know, and governments and military powers work continually to make them more so. Are we really in a position to congratulate ourselves on our sort of 'civilisation'? Another objection is that citizens have little say in the making of international law, which is done by governments. Rules that apply internationally are, in fact, dictated by the strongest states - and also by the power of the strongest multinational business organisations in the new globalised world. But many citizens do have the freedom (and choice) to make their voices heard, and new communications systems make this easier. The first thing to do is to collect the facts, and then start a public debate. International law, and the breaking of it, affects every human being on the planet.