What Is International Law?

Teaching Resources—Global Governance: Introduction (including lesson plan with slides)

What happens if someone breaks the law? They can be arrested, stand trial, and pay a fine or go to prison if found guilty.

What happens if a country breaks a law? The reality there looks quite different. The world has no global police force or international prison. If a country doesn’t like a certain law, it can simply choose not to follow that law. That makes holding countries accountable for their actions quite difficult.

This resource explores the origins of international law, the most important international agreements that bind it, the reasons countries sometimes break those rules, and the international courts that enforce them.

What is the history of international law?

Modern international law dates back to the turn of the twentieth century. Determined to usher in an era of peace and prosperity, world leaders gathered at The Hague—a city in the Netherlands—in 1899 and 1907 to establish the first laws of war and arms control agreements. The League of Nations (founded in 1920) was among the first international organizations dedicated to securing world peace and adjudicating international disputes. Despite those treaties and institutions, the world descended into two calamitous world wars in the first half of the twentieth century, dealing a devastating blow to the idealistic belief that international law alone could tame the world’s violence, expanding the rule of law of their own nations.

Nevertheless, in the aftermath of World War II, countries sought to ensure the world would never again experience such horrific conflict. In 1945, that effort led to the creation of the United Nations, whose founding document—the UN Charter—laid out rules whereby countries agreed to uphold human rights, respect borders, and settle disputes through negotiation and arbitration rather than conflict. Of course, that agreement hasn’t always worked out, and conflicts still occur—but so far another world war has been avoided.

The UN Charter is not the single rule book for international law. Since World War II, countries have signed numerous agreements on issues both mundane and profound, including nuclear proliferation, trade, fishing rights, climate change, outer space, the treatment of diplomats, and the rules of war. That body of rules and regulations is collectively known as international law.

Why do countries violate international law?

Ordinary citizens can’t simply pick and choose the laws that apply to them. Imagine someone agreeing not to commit murder but saying laws about robbery don’t apply to them.

International law, on the other hand, is based on voluntary buy-in. That means countries do in fact get to choose the laws that apply to them. If a government refuses to follow the latest climate accord, there’s little anyone else can do to hold that government accountable. But sometimes, those laws can help mobilize domestic groups that work to hold their governments to account or encourage their governments to sign new agreements.

Countries do not follow certain international laws for several reasons. Sometimes governments believe that international laws clash with their national interests. For example, North Korea withdrew from a treaty prohibiting nuclear weapons in 2003 because it claimed that acquiring nuclear weapons was necessary for its defense. Few, if any, instances exist in which a country would sacrifice its national interest to abide by international laws.

In other instances, countries argue that certain international laws violate their sovereignty—the principle that guarantees countries get to control what happens within their borders. The European Court of Human Rights (ECHR) has repeatedly convicted Russia of discriminating against the LGBTQ+ community, but the Russian government refuses to change its laws. It contends that an international court should not have the power to determine national laws that Russian citizens have not agreed to and do not wish to follow. In the United States, the Senate has repeatedly refused to ratify the UN Convention on the Law of the Sea because it believes the pact infringes on U.S. sovereignty. Still, the United States criticizes China for violating the accord.

Other countries cite discrimination as a reason for not following particular laws. The African Union—a regional political forum—encouraged its members to withdraw from the International Criminal Court (ICC), arguing that the court unfairly targets African countries in its human rights cases. Indeed, since the ICC’s founding in 2002, forty-four of the people indicted by the court have been African nationals. The ICC’s indictment of Russian President Vladimir Putin in 2023 was an unprecedented case and the first outside of Africa.

The ICC is one of several courts that adjudicate international legal disputes.

Let’s explore some of the world’s most prominent courts and see where they succeed and struggle in enforcing their rulings.

What is the International Court of Justice?

The International Court of Justice (ICJ), sometimes known as the World Court, is the official court of the United Nations. Headquartered in The Hague, the ICJ’s judges are elected by the UN General Assembly and Security Council and are responsible for resolving legal disputes between the United Nations’ 193 members on issues related to property rights, force, and diplomatic relations, among other issues.

The court has proved successful in resolving border disputes. In the 1990s, Cameroon and Nigeria clashed over Bakassi, a peninsula in the Gulf of Guinea that both countries claimed as their own. The two countries brought their dispute to the ICJ, which ruled in 2002 that Bakassi belonged to Cameroon. After several more years of UN-facilitated negotiations, Nigeria transferred control of the peninsula to Cameroon in 2008. Nevertheless, the world’s most heated territorial disputes are never brought before the ICJ, as neither party would risk losing its case.

The ICJ is also not always able to enforce its rulings. In 2003, the UN General Assembly asked the court to decide whether Israel’s construction of a wall alongside the occupied West Bank violated international law. In just months—a surprisingly quick decision for a court that usually takes years to issue rulings—the ICJ declared the wall was illegal and ordered Israel to stop construction. However, the Israeli government ignored the court’s decision and completed the wall, claiming it was necessary for defense, questioning the effectiveness of the international court. 

When countries disregard ICJ rulings, the court can ask the UN Security Council to determine the consequences. In the case of the wall, however, the United States—a permanent member of the UN Security Council with the power to block any resolution—sided with Israel, shielding the country from any repercussions for its actions.
 

What is the International Criminal Court?

The ICC is an independent court, also headquartered in The Hague, that is responsible for trying individuals accused of the most egregious human rights violations.

Despite that mandate, the ICC lacks serious enforcement powers, which severely limits its effectiveness. Since the court’s founding in 2002, it has tried thirty-one cases—only ten of which have resulted in convictions.

Given the absence of a global police force, the ICC struggles to bring individuals to trial. Former Sudanese President Omar al-Bashir has avoided standing trial for genocide, war crimes, and crimes against humanity since the ICC first issued a warrant for his arrest in 2006. Only because a 2019 revolution ousted Bashir from power does he now face the possibility of being turned over to the ICC.

Additionally, governments can simply withdraw from the ICC if they are under investigation—Burundi and the Philippines have done just that in recent years. In fact, nothing compels countries to join the ICC in the first place. Although every UN member is subject to the ICJ, only 123 countries have signed on to the Rome Statute, the ICC’s founding document. Notable absences include the United States, China, India, and Russia.
 

The United States even passed a law in 2002 that prohibits its allies from handing American citizens over to the court for prosecution. And when the ICC opened an investigation in 2020 into alleged American war crimes in Afghanistan, the White House imposed sanctions on ICC personnel and prohibited their entry into the United States. Nonetheless, the United States has used its position on the UN Security Council to have the ICC investigate individuals, including former Libyan dictator Muammar al-Qaddafi.

What is the European Court of Human Rights?

Founded in 1959, the ECHR is a regional court with members including Russia, Turkey, the countries of the European Union, and several others. Its mission is to uphold the European Convention on Human Rights.

The ECHR is a relatively fast-moving court that adjudicates disputes between countries and hears cases brought by individuals, companies, and nongovernmental organizations. Its landmark judgments have advanced the rights of minority groups within its member countries, including a 1988 ruling that paved the way for Ireland’s decriminalization of homosexuality.

Still, like other international courts, the ECHR faces enforcement challenges. Russia has ignored several ECHR rulings, claiming they violate the country’s sovereignty, and it is not alone. Member countries have failed to implement thousands of the ECHR’s rulings.

Nevertheless, the ECHR is an example for similar regional human rights courts around the world, including the Inter-American Court of Human Rights and the African Court of Human and Peoples’ Rights.

Do all international courts face enforcement challenges? 

In addition to the ICJ, ICC, and ECHR, dozens of courts and tribunals work to enforce international law. Some focus on particular regions, while others cover the entire globe; some tackle a wide range of issues, while others hear cases related to specific topics like trade, nuclear energy, or maritime disputes.

One commonality between those courts is the challenge of holding offenders accountable for their actions. Take the International Tribunal for the Law of the Sea. In 2016, the court ruled that China’s territorial claims to the highly contested South China Sea had no basis in international law. Despite that ruling, China has continued to militarize the region and has faced few, if any, consequences for its actions.

Although international law has facilitated negotiation and cooperation among countries on issues of global importance like trade and climate change, those agreements have their limitations. Most important, without a global enforcement mechanism, countries will never agree to sacrifice their national interests to comply with an international legal ruling.