International Jurisprudence: Treaties, Customary International Law, and Jus Cogens
In the vast landscape of international jurisprudence, the relationship between Treaties (written agreements) and Customary International Law (unwritten, universal practices) forms the backbone of global order. While treaties resemble contracts between nations, customary law represents the shared conscience of the international community. At the apex of this hierarchy lies Jus Cogens—peremptory norms from which no derogation is permitted. Understanding how these distinct sources of law collide, overlap, and reinforce one another is essential for grasping how justice is administered on a global scale.
Defining the Pillars: Treaties vs. Customary International Law
Before exploring their relationship, we must define the two primary sources of international law as outlined in Article 38(1) of the Statute of the International Court of Justice.
Treaties (Conventional Law)
- These are formal, written agreements between states (e.g., The UN Charter, The Geneva Conventions).
- They only bind the states that sign and ratify them (the principle of pacta sunt servanda).
Customary International Law (CIL)
- This arises from a general and consistent practice of states followed by them from a sense of legal obligation (Opinio Juris).
- Unlike treaties, CIL can bind all states, regardless of whether they signed a document.
Illustrative Example
Example: While a specific treaty might ban plastic waste in the Mediterranean, the broader prohibition against “significant transboundary environmental harm” is considered a rule of Customary International Law that applies to all nations.
The Concept of Jus Cogens: The “Super-Norms”
Jus Cogens (Latin for “compelling law”) refers to fundamental principles of international law that are so universally accepted that they can never be set aside. Under Article 53 of the Vienna Convention on the Law of Treaties (VCLT), any treaty that conflicts with a jus cogens norm is void.
Commonly Recognized Jus Cogens Norms
- The prohibition of genocide.
- The prohibition of slavery.
- The prohibition of torture.
- The prohibition of wars of aggression (illegal use of force).
The Relationship Dynamics: How They Interact
The relationship is not competitive but symbiotic. They often move through two processes:
Codification (Custom to Treaty)
This occurs when a long-standing custom is written down into a formal treaty to provide more clarity and precision.
Case Reference: In the North Sea Continental Shelf Cases (1969), the ICJ looked at whether the “equidistance principle” for maritime boundaries had moved from a custom into the 1958 Geneva Convention.
Generation (Treaty to Custom)
Sometimes, a rule starts in a treaty but becomes so widely accepted that it turns into a custom, binding even those who never signed the treaty.
Case Reference: In the Nicaragua v. United States (1986) case, the ICJ held that the prohibition on the use of force, while written in the UN Charter (a treaty), also existed independently as Customary International Law.
Conflict of Laws: When Treaties Meet Jus Cogens
What Happens When a Treaty and a Custom Say Different Things?
- Lex Specialis: Generally, a specific treaty takes precedence over a general custom.
- The Jus Cogens Exception: If a treaty provision violates a jus cogens norm, the treaty is automatically “null and void.” No two states can legally agree to commit genocide or engage in human trafficking via a treaty.
Practical Example
If Country A and Country B sign a “Mutual Defense Treaty” that includes a secret clause to systematically exterminate an ethnic minority in a border region, that treaty is legally non-existent under international law because it violates the jus cogens prohibition of genocide.
Leading Case Law
To understand these concepts, we must look at how the courts have ruled:
The Barcelona Traction Case (1970)
This case introduced the concept of erga omnes obligations—obligations owed to the international community as a whole. The court suggested that because certain customs (like the prohibition of aggression) are so important, every state has a legal interest in their protection.
Questions Relating to the Obligation to Prosecute or Extradite (Belgium v. Senegal, 2012)
The ICJ explicitly confirmed that the prohibition of torture is a part of Customary International Law and has attained the status of jus cogens. This means Senegal could not use its internal laws or lack of treaty ratification to avoid its obligation to address alleged torture.
Vlastimir Đorđević v. Prosecutor (ICTY)
In criminal law contexts, courts frequently cite the jus cogens nature of crimes against humanity to justify why “statutes of limitations” (time limits for prosecution) do not apply.
Summary Comparison Table
| Feature | Treaty Law | Customary Law (CIL) | Jus Cogens |
|---|---|---|---|
| Form | Written | Unwritten / Practice | Fundamental Norm |
| Consent | Explicit (Ratification) | Implicit (State Practice) | Universal (Non-consensual) |
| Flexibility | States can “Opt-out” | “Persistent Objector” Rule | No Derogation Allowed |
| Legal Status | Binding on Parties | Binding on All (Mostly) | Supreme Authority |
Conclusion
The relationship between treaties and customary international law is one of constant evolution. Treaties provide the “black letter” clarity that modern diplomacy requires, while customary law ensures that even in the absence of a signature, states are bound by basic standards of humanity. Jus cogens acts as the ultimate safeguard, ensuring that no treaty—no matter how formally correct—can legalize acts that shock the conscience of mankind. For the student of law, recognizing that a treaty is often just a “snapshot” of an evolving custom is the key to mastering international jurisprudence.
Written By: Judge Nazmul Hasan
Senior Judicial Magistrate | Prime Minister Gold Medalist
Profile Overview
p>Nazmul Hasan is a highly accomplished judicial officer and legal scholar from Bangladesh, distinguished by a rare blend of judicial service excellence and unparalleled academic achievement.
Professional Expertise
| Title | Achievement / Service | Details |
|---|---|---|
| Senior Judicial Magistrate | Bangladesh Judicial Service (BJS) | Serving as a Senior Judicial Magistrate, demonstrating profound expertise in dispensing justice and administering court procedures. |
| Service Rank | 11th Bangladesh Judicial Service (BJS) | Secured the 7th Merit Position overall in the rigorous 11th BJS competitive examination, marking an exceptional start to a distinguished judicial career. |
Academic Distinction
| Qualification | Institution | Recognition |
|---|---|---|
| LL.B. (Hons.) | University of Rajshahi | First Class First (Top of the Cohort), signifying ultimate academic mastery in undergraduate legal studies. |
| LL.M. | University of Rajshahi | Achieved First Class standing, further solidifying expertise and specialized knowledge in advanced legal disciplines. |
Honors & Achievements (Awards of Excellence)
- Prime Minister Gold Medalist (2017)
Awarded the nation’s most prestigious academic honor for outstanding performance across all disciplines at the university level. - Agrani Bank Gold Medalist for Academic Excellence (2023)
Recognized with this distinguished medal for sustained academic excellence and leadership in the field of law.
Contact Information
Email: [email protected]
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