International law — also called public international law, or the “law of nations” — is the body of rules, norms and standards that apply to sovereign states when they interact with one another. It has diversified considerably since the end of World War II, when a host of multilateral contracts, treaties and conventions on topics as diverse as outer space, the treatment of diplomats, climate change, and the rules of war gave rise to new areas of international law.

Today, international legal norms govern many aspects of global life: worldwide telecommunications and postal networks; universal recognition of time standards; improved weather forecasting; stricter safety standards for cars and planes; the sharing of information about the origins of food and other products; intellectual property protection for software, literary and artistic works, and the tracing of human trafficking, drug smuggling and other criminal activity across borders. While governments may choose not to abide by these agreements, violations of certain peremptory norms can be met with disapproval or even coercive action ranging from diplomatic and economic sanctions to military intervention.

While it’s easy to be skeptical that these global rules and norms have any real power, most people will engage with international law at some point — whether as members of multinational corporations or consumers of goods produced by foreign companies; immigrants seeking asylum from strict totalitarian regimes; or sailors sailing the oceans under the watchful eye of admiralty laws. It’s important that these individuals understand the power and purpose of international law.