Sources of International Law

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  • 0:01 Why Have International Law?
  • 0:44 Treaties
  • 1:31 International Traditions
  • 2:50 The United Nations
  • 4:05 Past Rulings & Legal Scholars
  • 5:26 Lesson Summary
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Lesson Transcript
Instructor: Kevin Newton

Kevin has edited encyclopedias, taught history, and has an MA in Islamic law/finance. He has since founded his own financial advice firm, Newton Analytical.

You often hear people talking about the importance of international law, but where does it come from? This lesson explains many of the sources of international law, from ancient treaties to modern courts.

Why Have International Law?

Imagine an elementary school during recess. You've got a whole mix of children, from popular kids to unpopular kids, big kids to little kids of all ages and social abilities, all playing under the watchful eye of a group of teachers. Now, remove the teachers. It gets pretty chaotic pretty quickly, doesn't it? Eventually, some form of order would be established between groups of children - after all, one bully can't control the entire playground!

This is similar to how international law works. Noting that it was impossible for one country to rule the entire world, or even to govern most of it, various nations have made agreements throughout history to help set rules of proper behavior for everyone.


By far the oldest agreements around are treaties. There are still treaties in effect from almost 700 years ago! A treaty is an agreement between two or more parties that sets expected behavior. Most often today, this is some sort of peace treaty, but it can take different forms. For example, trade agreements, by which two or more countries agree to work to exchange goods with each other, are the international relations equivalent of offering to trade one's milk at lunch for an extra cup of pudding.

Still, treaties can cover a wide range of topics. Take, for example, that 700-year-old treaty I referred to earlier. It is a military alliance, or an agreement for one country to assist the other if attacked by a third party. It was signed between Portugal and England as a form of deterrence against a common enemy: the Moors. In the years since, it has been used against everyone from the Spanish to the Germans.

International Traditions

Treaties often involve months of negotiation between parties, and especially when it's a peace treaty, the countries may not exactly like one another. Even when there is a peaceful relationship, diplomats often have to remain resident in places far away from home. In either event, international traditions play an important role. International traditions are those practices that accompany the treatment of diplomats and other foreign dignitaries. In short, it is the ultimate promise not to shoot the messenger.

In fact, a promise of safe travels for diplomats is a crucial part of diplomacy, and is a universal international tradition. To this end, diplomats in foreign countries enjoy diplomatic immunity, by which they cannot be arrested by local law enforcement for a wide range of offenses. Needless to say, this is an important perk of being a diplomat! However, before you start thinking that being a diplomat is the cure for any latent kleptomaniac tendencies, you should know about the idea of declaring someone a persona non grata. This is how a host country can get rid of a troublesome diplomat. Essentially, this declaration says to the diplomat's home country that they are no longer welcome in the host state.

The United Nations

Treaties and international traditions are a great way to make sure that common ground is established by countries for things that have already been discussed or mandated. However, what about more pressing issues? Or, better yet, what about issues that multiple countries share in having against a single offender state? This is a prime example of the usefulness of the United Nations, which has for more than 70 years served as an arbitrator of international disputes.

In fact, it is through the United Nations and its various administrative bodies, most notably the International Court of Justice, the United Nations has doled out many of the actual international legal opinions of the past few decades. However, the main apparatuses of the United Nations still have very important roles to play. The General Assembly of the United Nations, a council comprised of every U.N.-recognized state in the world, can pass non-binding resolutions. These have no enforceability, but are a form of persuasion, nonetheless.

After all, few countries like to be embarrassed by having been hit with a non-binding resolution. The U.N. Security Council, comprised of the United States, Russia, China, France, United Kingdom, and ten other rotating states, can pass binding resolutions. Binding resolutions carry the promise of economic sanctions or even military involvement.

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