International Law: Domestic Legal Systems And Their Applications

International law is a set of rules, norms, and standards that govern the conduct and relations of sovereign states, international organisations, and individuals. While it operates largely through consent, as there is no authority to enforce it, international law differs from state-based domestic legal systems in its application. The relationship between the two is complex and variable, with states adopting either a monist or dualist approach. Monist systems automatically incorporate international law into national law upon ratification, whereas dualist systems require translation into national legislation for domestic application.

Monist and dualist systems

The terms monism and dualism describe two theories of the relationship between international law and domestic law. Monism and dualism offer different approaches to how international law comes into effect within states, and how conflicts between national and international law are resolved.

In a monist system, international law does not need to be translated into national law. The act of ratifying an international treaty immediately incorporates that law into national law. International law can be directly applied and adjudicated in national courts. Monist systems differ in their approach. Under some constitutions, direct incorporation of international obligations into domestic law occurs upon ratification. In other states, direct incorporation occurs only for self-executing treaties.

In a dualist system, international law is not directly applicable domestically. It must first be translated into national legislation before it can be applied by the national courts. Therefore, for a dualist state, ratification of an international treaty is not enough, and national implementing legislation is necessary.

In practice, many states are partly monist and partly dualist in their actual application of international law in their national systems. The United States, for example, has a "mixed" monist-dualist system. International law applies directly in US courts in some instances but not in others.

International law and municipal law interface

The relationship between international law and municipal law rests on two principal schools of law: monism and dualism.

Monism assumes that international and municipal law are part of the same legal order. In states with a monist system, international law does not need to be translated into national law. The act of ratifying an international treaty immediately incorporates that international law into national law. For instance, in the Netherlands, a monist system, the International Criminal Court (ICC) Statute can be directly applied and adjudicated in national courts. However, the view of the Netherlands is that as a state party, it is obliged to implement the statute through national legislation.

Dualism, on the other hand, considers national and international law as two separate legal orders. In states with a dualist system, international law is not directly applicable domestically and must be translated into national legislation before it can be applied by the national courts. For example, in the United States, a dualist system, ratified human rights treaties and customary international law are both law of the land. Unless a court deems a treaty to be self-executing, it will bind domestic courts only if Congress has passed legislation to implement the treaty provisions domestically.

While the relationship between international and municipal law is complex and variable, four main methods are generally available for the implementation of international human rights instruments in domestic law:

• Direct incorporation of rights recognised in international instruments into a bill of rights in the national legal order.
• Enactment of different legislative measures in civil, criminal, and administrative laws to give effect to the different rights recognised in human rights instruments.
• Self-executing operation of international human rights instruments in the national legal order.
• Indirect incorporation as aids to interpret other law.

Self-executing treaties

The distinction between self-executing and non-self-executing treaties first emerged in the early 19th century in the United States, where it has been a source of confusion for courts. Since then, the distinction has been adopted by the courts of other countries.

Most scholars in the United States view a treaty's self-executing character as solely a matter of domestic law. This view is supported by the fact that, under the constitutional law of some states, treaties may not be enforced by the courts without implementing legislation. However, non-US scholars have taken the position that a treaty's self-executing character is a matter of international law. This position finds some support in statements by international adjudicatory bodies that certain treaties are self-executing.

The determination of whether a treaty is self-executing depends on the intention of the signatories and the interpretation of the courts. For example, in Sei Fujii v. State of California (1952), the California Supreme Court held that the UN Charter was not self-executing because its principles concerning human rights lacked the mandatory quality and certainty required to create justiciable rights for private persons upon ratification.

In monist systems, such as the United States, international law does not need to be translated into national law, and self-executing treaties apply directly as part of the supreme law of the land. In contrast, dualist systems, such as the United Kingdom, require international law to be translated into national legislation before it can be applied by the national courts.

Jus cogens

There is no universal agreement on which norms are jus cogens or how a norm reaches that status. However, it is generally accepted that jus cogens bans certain practices, including maritime piracy, slavery, wars of aggression, territorial aggrandizement, and torture.

The concept of jus cogens, or peremptory norms, was established by the adoption of the Vienna Convention on the Law of Treaties in 1969. Under Article 53 of the Convention, any treaty that conflicts with a peremptory norm is void. The Convention also allows for the emergence of new peremptory norms, but does not specify what these are.

The number of peremptory norms is considered limited but not exclusively catalogued, and they arise out of case law and changing social and political attitudes. While there have been attempts to classify certain rules, rights, and duties as peremptory norms, these attempts have not been very successful.

Domestic enforceability of customary international law

The domestic enforceability of customary international law is a complex issue that varies across different legal systems. Customary international law refers to international obligations that arise from established or usual international practices, which are less formal and often unwritten, as opposed to formal written treaties or conventions. It is one of the primary sources of international law, alongside treaties and general principles of law.

Customary international law becomes binding when two requirements are met: a widespread and consistent state practice, and the belief that there is a legal obligation to follow the rule (opinio juris). The International Court of Justice (ICJ) has confirmed that these two elements are essential. While many governments accept the existence of customary international law in principle, there are differing opinions on the specific rules it contains.

The domestic enforceability of customary international law depends on the approach taken by a particular country's legal system. There are two main approaches: monism and dualism.

Monist systems automatically incorporate international law into national law upon ratification. In these systems, international treaties can be directly applied and adjudicated in national courts without the need for additional legislation. However, it is important to note that monist systems can differ in their approach. Some directly incorporate international obligations into domestic law upon ratification, while others do so only for self-executing treaties.

On the other hand, dualist systems require international law to be translated into national legislation before it can be applied by national courts. In these systems, the ratification of an international treaty is not sufficient, and implementing legislation is necessary. War crimes trials, for example, can only take place when the relevant national legislation is enacted unless such legislation already exists.

The United States provides an example of a dualist system. Unless a court deems a treaty to be self-executing, it will bind domestic courts only if Congress has passed legislation to implement the treaty's provisions domestically. The Supremacy Clause of the U.S. Constitution makes ratified human rights treaties and customary international law the "Supreme Law of the Land," binding on federal, state, and local governments.

In contrast, the Netherlands exemplifies a monist system. After signing and ratifying the Rome Statute, the Dutch government enacted implementing legislation to give the statute domestic effect. This legislation provided a statutory basis for transferring suspects to the International Criminal Court (ICC) and cooperating with the ICC.

While monist and dualist systems offer different approaches to the domestic enforceability of customary international law, it is worth noting that the relationship between international and national law is complex and variable. The specific methods for implementing international law into domestic legal systems can vary across countries, and there may be variations even within the monist and dualist systems.

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