International law is the body of rules and general principles that nations are expected to observe in their relations with one another. Some international laws result from years of custom. Others originate in general principles of law recognized by civilized nations. Still others have been agreed to in treaties or determined by judicial decisions.
Many of the customs of international relations have existed for hundreds of years. For example, the ancient Greeks protected foreign ambassadors from mistreatment, even in wartime. For about 2,000 years, nations have given ambassadors similar protection.
Treaties or contracts between countries have been in use for thousands of years. Such treaties as the one that established the Pan American Union may be signed by many nations. Or they may be signed by only two or three nations, as in the case of trade treaties the United States has signed with other countries.
