The debate over how customary international law (CIL) applies to ‘holdout’ states is both intricate and deeply thought-provoking. A ‘holdout’ state is essentially one that refuses to follow a customary international rule, even when most other nations accept and practice it. This situation raises big questions about whether consent is necessary and whether CIL should be considered universally binding.

Here are some of the core issues:

The Question of Consent: CIL is built on two main ideas—states acting consistently in a certain way and believing they’re legally obligated to do so (opinio juris). But what happens when a state doesn’t agree with or contribute to a norm’s development? Can that state still be bound by it? Some believe CIL applies to all nations automatically, while others argue it only binds those who actively accept it.

The Challenge of Holdout States: States that reject customary norms throw a wrench into the idea of universal application. For these states, refusing to comply might be a way of asserting their independence and sovereignty. However, critics say that allowing holdouts undermines the idea that CIL applies equally to everyone. This brings up the tricky question of whether states can opt out of norms or are obligated to follow them anyway.

The Problem of Ambiguity: CIL is often criticized for being too vague. It’s not always clear when a norm becomes part of customary law or what its specific requirements are. This lack of clarity makes it harder to justify enforcing these norms, especially when some states challenge their legitimacy.

Are Customary Norms Universal?: One of the big questions is whether CIL should apply to all nations, or just those that consent. Supporters of universality argue that some norms—like banning slavery or genocide—are so important that they must bind all states, no exceptions. On the flip side, others say that respecting state sovereignty means only applying norms to those that explicitly agree to follow them.

Broader Critiques of CIL: Beyond the holdout issue, CIL itself has been called into question. Critics say it’s too flexible and often shaped by the interests of powerful nations. Some even argue that it’s outdated and that international law should rely more on formal treaties, which are clearer and ensure broader participation.

In short, the tension between CIL and holdout states touches on fundamental issues about consent, fairness, and the universality of international norms. This isn’t just a theoretical debate—it affects how international law is interpreted and enforced in critical areas like human rights, environmental protection, and global security.

The distinction between Opinio Juris and Customary Law

The distinction between opinio juris and customary law lies in their role in the formation of legal norms in international law. Opinio juris is the belief by states that a particular practice is carried out because it is legally required, serving as the subjective element in the creation of customary law. In contrast, customary law is the binding legal rule that arises when opinio juris is combined with consistent and widespread state practice (the objective element).

Example:

• Opinio Juris: States believe they are legally obligated to grant immunity to foreign diplomats because international law requires it, not merely as a courtesy.
• Customary Law: Diplomatic immunity has become customary international law because most states consistently grant this immunity (state practice) and do so out of a recognized legal obligation (opinio juris).

If a state grants immunity to diplomats only out of tradition or political convenience, the requirement of opinio juris is missing, and the practice does not contribute to the development of customary law. Customary law results only when both elements—consistent practice and the belief in a legal obligation—are present.