International law may also affect companies, international organisations and individuals. Unlike national law, international law is a horizontal legal system in which the rules of law are created and enforced by the States themselves. This is done by the States giving their consent to be bound by a certain rule, usually in written form as a treaty (e.g. in agreements, conventions, or protocols), or through practice (referred to as customary international law). The starting point is that States are sovereign and legally equal to each other.
Research in this area is often interdisciplinary. Examples of obvious issues relevant for international law are how a state has the right to exercise power within its own territory, the extent to which the international community can control and interfere with how a state treats its inhabitants, and how a state can be held responsible under international law for an act or omission. Other issues may overlap with other areas of law, such as what rights and obligations a state has for oceans or the environment, or how individuals responsible for serious violations of international law can be brought to justice (procedural law and criminal law).
