The Importance of International Law

International law defines the legal responsibilities of States in their interactions with each other and their treatment of individuals within State boundaries. It also regulates the global commons, such as air, sea, outer space and world trade.


The study of international law involves understanding the way that a country’s leaders and citizens understand its role. It is important that they internalize international law, and that they feel obligated to follow it.

Sovereignty of States

Sovereignty is the underlying principle of international law that states have an absolute right to determine their own internal and external affairs without any interference from other nations. This concept of sovereignty was established in the 16th century by Jean Bodin, who used it to bolster the power of French kings over rebellious feudal lords and thereby facilitate the transition from feudalism to nationalism.

The modern day world of international law has many different aspects that affect sovereignty, including economic globalisation and the rise of supranational institutions. These developments, along with the emergence of human rights, have placed restrictions on sovereign power by enshrining individual rights and freedoms vis-A-vis the state.

Nevertheless, it is also true that the current legal system still relies on sovereign will and consent to determine which international rules apply. While this may have worked in the past for Western powers, it is no longer the case in the post-colonial world. The ad hoc manner in which international laws are developed and implemented, combined with the often-debatable enforcement mechanisms, mean that they have proven to be less than effective. This is because they have been constructed to marginalise the non-West and limit their influence over international law. This has made it difficult for the international community to agree on a common approach to international law, which would be based on mutual benefit and reciprocity.

International Organizations

International organizations are a vital feature of today’s world. Whether they are helping to build houses for the poorest of the poor, as UN-Habitat does; working to ensure that everyone has access to safe drinking water, as the World Health Organization does; or promoting global economic stability and prosperity, as the International Monetary Fund and the World Bank do, they affect our lives in profound ways. Yet, until recently, they have received relatively little analytical attention.

The prevailing view has been that, despite the fact that they may have their own internal legal systems, international organizations are bound by international law and can be held liable for violations of that law. The main challenge is to determine the extent to which that view is correct. The answer lies in recognizing that there are two categories of relations between an international organization and its members: those that take place on the international plane and those that are, rather, situated on the institutional plane constituted by the organization’s own rules.

The first category of relations is covered by the general legal principles and instruments of international law. These can be supplemented by the internal legal system of an organization, as well as by specific conventions, treaties and agreements. The second category of relations, however, is a matter of customary law.


Treaties are agreements between sovereign states or other entities with international personality, such as intergovernmental organizations. They are normally signed and require ratification. A treaty may be subject to a modus vivendi clause, which suspends its operation but does not release the parties from their obligations under it. Modern treaties often contain articles governing where the final authentic copies will be deposited and how any disputes as to the interpretation of the treaty will be peacefully settled.

Some treaties are self-executing, requiring only the signature of the parties to put them into effect. Others are non-self-executing and require that implementing legislation be passed in the signatory states to enable them to meet their treaty obligations. Non-self-executing treaties also typically include provisions for the modification of certain treaty provisions, which are permitted only if they do not alter the rights, obligations and legal situations that have been established by the treaty or do not contravene its object and purpose.

Studies of treaty effects have shown that they can be larger than expected at the time of their negotiation, but smaller or absent when evaluated in terms of their ratification or coming into force. This suggests that immediate socialization and short-term normative processes are more important to the effectiveness of a treaty than longer-term legal process such as ratification or the emergence of enforceable international law.

International Courts

Among the most important institutions for international law are the world’s international courts. These tribunals prosecute individuals for major crimes and settle disputes involving international law. They also investigate and monitor human rights violations. Some international courts also act as arbiters in peace and wartime.

In addition, many courts have a significant impact on the development of international law through their case law and advisory opinions. Some courts have even established doctrines that become widely accepted, resulting in the creation of new legal rules.

The most famous international court is the International Court of Justice (ICJ), the principal judicial organ of the United Nations. It is a permanent, international body of 15 judges—no two may be nationals of the same country—elected to nine-year terms. The ICJ has issued important decisions and opinions on issues such as the law of the sea, territorial integrity, and the legality of the threat or use of force.

While the ICJ’s decisions are not binding, it has considerable influence. Moreover, judges of other international tribunals often refer to the ICJ’s case law when developing their own decisions. In fact, a number of scholars have argued that these decisions form part of the common law of international law. See, for example, Antonio Cassese, ‘The Influence of the ICJ on International Criminal Tribunals’ in Morten Bergsmo and Samuel Gutman (eds), Human Rights and Conflict in the 21st Century: Essays in Honor of Asbjorn Eide, Brill Nijhoff, 2004.