Treaty law covers treaties and conventions that States opt to sign or not. Customary law, on the other hand, is a set of general internationally applicable rules by which all States – and even non-State actors – are bound. It applies to all parties in a conflict, and in all areas in the conflict (with a few very specific regional variations). If enough States follow a certain practice, and the international community believes that such practice is required as a matter of law, then a law may become ‘customary’. Another name for International Humanitarian Law (IHL) is the Laws of Armed Conflict (LOAC).
The primary foundation of International Humanitarian Law (IHL) is the Geneva Conventions of 1949 and Additional Protocols of 1977. The ICRC defines IHL as set of rules which seek to limit the effects of armed combat by protecting those who are not, or who are no longer, taking part in hostilities, and by regulating methods of warfare. It tries to strike a balance between legitimate military action and the humanitarian objective of reducing human suffering.
The key areas of IHL are: