Understanding Customary International Law and Domestic Legal Systems

It's important to know how customary international law (CIL) works with the laws in our own countries. CIL includes practices and customs accepted by many countries as rules that everyone should follow, even if they aren't written down. This brings up big questions about how these rules fit into the laws of each country and how they're enforced or recognized.

To understand this, we first need to look closely at what customary international law is all about. CIL has two main parts: state practice and opinio juris.

• State Practice: This means how countries behave consistently.
• Opinio Juris: This is the belief that those behaviors are legally required.

For example, the rule against torture is a strong part of customary international law. Many countries not only follow this rule, but they also believe it’s a legal duty to do so.

When we talk about how CIL interacts with the laws in different countries, there are mainly two ways this is done:

1. Monism

• In monist countries, international law and domestic law are seen as one single system.
• Once a rule of customary international law is accepted, it automatically becomes part of the country's laws without needing new laws to be made.
• Countries like the Netherlands and Germany follow this approach. In these places, once people recognize a custom internationally, they can use it directly in their courts.

2. Dualism

• On the other hand, dualist countries keep international law and domestic law separate.
• Here, customary international law doesn't automatically become part of the country's laws. It has to be specifically added through new laws.
• The United Kingdom is an example of a dualist system. In this case, customary international law isn’t effective until Parliament turns it into national law.

Additionally, whether customary international law is binding can depend on certain principles, like state consent and the power of domestic courts. While most countries agree to follow these international customs, how they enforce them can be very different.

A key factor to look at is how judges and courts handle these customs. Some courts may be more willing to use or recognize international rules. In many places, judges refer to international laws when making decisions, especially when their own laws require them to follow international standards. For instance, courts in Canada and South Africa often try to interpret their laws while considering international practices.

Judicial activism can also impact how customary international law is included in national laws. Sometimes, courts choose to use CIL as a reason for their decisions, strengthening the role of these rules where they work.

Some countries create a system called "transformation," where customary international law needs specific national laws to be enforced. Courts may find themselves juggling the need to align local laws with international ones while acknowledging their own national independence.

Here's how the relationship between customary international law and domestic law can show up:

• Direct Application: In some countries, people can take customary international law directly to the courts. For example, laws about human rights are often used to help individuals claim their rights.

• Interpretive Guidance: Even in countries with a dualist approach, courts might refer to customary international law to help explain what domestic laws mean, especially when those laws are unclear.

• Integration in Legislation: Many countries choose to write new laws that match customary international norms. Issues like human rights and environmental protection now reflect these international standards, influencing domestic policy.

But this relationship can be tricky. Problems can happen when local laws clash with customary international law, leading to questions about which laws are more important. Courts might face tough choices when local interests conflict with international obligations.

The principle of sovereign immunity can also make applying CIL difficult. For example, even though international law sets up rules for holding people accountable for serious crimes, such as war crimes, local courts might find it hard to prosecute someone because of their own legal rules about sovereignty.

In short, the connection between customary international law and domestic legal systems is complex. As the world changes and issues cross borders, understanding this connection is becoming even more important.

In conclusion, looking at this relationship helps us see bigger ideas about how laws are created and enforced. By understanding how customary international law interacts with local laws, countries can show their commitment to international standards, building a more united global community that respects law and human rights.