Principles of International Law: a brief guide

International law in context

International law, in general, sets out the rules that apply to the relationships between states. It also sets out rules on many issues that states have agreed are of international importance. International law covers a lot of things. These are just a few examples:

• Human Rights
• International peace and security
• International trade
• International Crimes (Genocide, Crimes Against Humanity, War Crimes)
• The Law of War (also known as International Humanitarian Law)
• Diplomatic relations
• Extradition
• Investment treaties
• Economic development
• Climate change
• International dispute settlement
• International monetary affairs
• Double Taxation Treaties

International legal obligations come from a number of different sources, including treaties, international customary law, general principles of law and United Nations resolutions. Individual states take different approaches to their international obligations. Some treat international law as part of their domestic law. Others (including the UK) see international law as separate to domestic law, and require domestic legislation to implement international obligations.

Disputes and breaches of international law

The 1969 Vienna Convention on the Law of Treaties (VCLT) sets out the rules relating to the formation, termination, conclusion, interpretation, and validity of treaties. Most treaties provide their own consequences and dispute settlement procedures for a breach of the rules they set out.

There are many examples in international affairs of disputes going unresolved, or allegations of breaches of international law that are never formally adjudicated and decided upon. Some examples are provided in this paper. The paper is not intended to be exhaustive in nature, and there are many institutions and legal systems not covered here.