In an increasingly interconnected world, legal systems no longer operate in isolation. Countries engage with one another through trade, diplomacy, human rights agreements, environmental commitments, and international organisations. At the centre of these interactions is public international law, a body of legal principles and rules that governs relationships between states and other international actors.
For South Africa, public international law plays an important role in shaping legislation, guiding judicial decisions, and ensuring the country meets its obligations on the global stage. Understanding how it works is essential for legal professionals, policymakers, and anyone interested in the development of modern law.
What is public international law?
Public international law is the branch of law that regulates the relationships between sovereign states, international organisations, and, in some cases, individuals and other entities operating within the international community.
Unlike domestic law, which governs the conduct of individuals and organisations within a country's borders, public international law focuses on issues that cross national boundaries. These may include matters such as human rights, international trade, diplomatic relations, environmental protection, armed conflict, and maritime law.
The primary sources of public international law include international treaties, customary international law, general principles of law recognised by nations, and decisions of international courts and tribunals.
The importance of public international law
Public international law provides a framework that allows countries to cooperate and resolve disputes peacefully. Without agreed legal standards, international relations would be far more unpredictable and potentially unstable.
By establishing common rules and expectations, public international law helps promote peace, security, economic cooperation, and respect for fundamental human rights. It also creates mechanisms through which states can address shared challenges, including climate change, migration, global health crises, and international crime. In today's globalised environment, few legal issues remain purely domestic. As a result, public international law continues to grow in importance.
Public international law and South African law
South Africa has a unique relationship with public international law. The Constitution recognises the importance of international legal principles and provides guidance on how they should be applied within the country's legal framework.
Section 39(1)(b) of the Constitution of the Republic of South Africa states that courts "must" consider law when interpreting the Bill of Rights, while foreign law "may" be considered. International law refers to international treaties and agreements South Africa has signed, ratified or acceded to, while foreign law refers to the domestic legal systems of other States, such as the UK, Australia, France and the USA. Section 233 of the Constitution further states that a court must prefer a "reasonable interpretation of legislation that is consistent with international law," over an alternative interpretation that would be inconsistent with international law.
This approach reflects the country's commitment to democracy, human rights, and the rule of law following the constitutional transformation of the 1990s.
International agreements entered into by South Africa may also become part of domestic law once they have been properly approved and incorporated through the relevant legal processes as contained in section 231 of the Constitution. This constitutional recognition ensures that public international law can influence legal development while maintaining the authority of South Africa's own legal system.
The influence of public international law on human rights
One of the most significant areas where public international law affects South African law is human rights. South Africa is party to numerous international human rights instruments that promote equality, dignity, freedom, and justice. These international commitments often assist courts in interpreting constitutional rights and resolving legal disputes.
When courts encounter uncertainty regarding the meaning or scope of a right contained in the Bill of Rights, international legal principles can provide valuable guidance. This helps ensure that South African human rights protections remain aligned with globally recognised standards. As a result, public international law contributes to the ongoing development and strengthening of constitutional democracy in South Africa.
The benefits of standardised public international law
One of the greatest advantages of public international law is the creation of shared standards across different countries.
When nations operate according to similar legal principles, international cooperation becomes more effective. Businesses can trade more confidently, governments can collaborate more easily, and individuals can enjoy greater legal certainty when interacting across borders. Standardised public international law also assists in protecting vulnerable groups and promoting universal values such as human rights, equality, and access to justice.
In addition, common legal standards help address global challenges that cannot be solved by one country alone. Issues such as environmental protection, cybercrime, terrorism, and public health require coordinated international responses, and public international law provides the framework for that cooperation.
Challenges facing public international law
Although public international law offers many benefits, it also faces several challenges.
One of the most significant difficulties is enforcement. Unlike domestic legal systems, there is no single global government responsible for enforcing international law. Compliance often depends on the willingness of states to honour their commitments.
Differences in political priorities, economic interests, and cultural perspectives can also create disagreements regarding the interpretation and application of international legal principles.
Despite these challenges, public international law remains an essential tool for maintaining international order and promoting cooperation among nations.
Why legal professionals should understand public international law
For legal practitioners, a solid understanding of public international law is becoming increasingly important. Many legal matters now involve international elements, whether through cross-border business transactions, international human rights issues, migration matters, or multinational regulatory frameworks.
An understanding of public international law enables legal professionals to better advise clients, interpret legislation, and engage with evolving legal developments. It also provides valuable insight into how domestic legal systems interact with the broader international legal community.
As South Africa continues to participate actively in international affairs, knowledge of public international law will remain a valuable skill for lawyers, judges, academics, and policymakers alike.
Conclusion
Public international law plays a vital role in regulating relationships between nations and promoting cooperation on issues that affect the global community. In South Africa, its influence is seen in constitutional interpretation, human rights protection, and the development of domestic legal principles.
By creating shared legal standards and encouraging international collaboration, public international law helps foster stability, accountability, and respect for fundamental rights across borders. While challenges remain, its importance in an interconnected world cannot be overstated.
For those interested in expanding their understanding of the law and other important legal disciplines, the Gawie le Roux Institute of Law offers practical legal training designed to deepen legal knowledge and support professional development. Investing in ongoing legal education is an excellent way to stay informed about the evolving relationship between South African law and the international legal system.
FAQs
What is public international law?
Public international law is the body of legal rules and principles that governs relationships between states, international organisations, and other international actors. It regulates matters such as human rights, international trade, diplomacy, and environmental protection.
What is international law in South Africa?
International law in South Africa refers to the international legal principles, treaties, and customary rules that influence and interact with the country's legal system. The Constitution recognises the importance of international law and makes it an imperative for courts to consider it when interpreting legal rights, obligations and human rights.
Who is the father of public international law?
Hugo Grotius, a Dutch jurist and philosopher, is widely regarded as the father of public international law because of his influential writings on the legal principles governing relations between states.
What is another name for public international law?
Public international law is sometimes referred to as the law of nations, a term traditionally used to describe the legal rules governing relationships between sovereign states.
Last updated on 2 July 2026.