Jus Cogens vs Erga Omnes: Differences and Cases
Jus cogens and erga omnes describe different features of international law. Jus cogens concerns a rule’s peremptory status: States cannot lawfully agree to depart from it. Erga omnes concerns an obligation owed to the international community as a whole, in whose protection all States have a legal interest. A peremptory norm gives rise to erga omnes obligations, but the two expressions are not interchangeable.
The prohibition of genocide illustrates the distinction. Its peremptory character prevents States from making a valid agreement authorizing genocide. Its erga omnes character means that compliance concerns all States, including those whose territory or nationals have not been directly affected.
Neither description, by itself, gives a court jurisdiction or decides which enforcement measures are lawful. Keeping those questions separate is essential when reading international judgments or answering an examination question.
What does jus cogens mean in international law?
Jus cogens refers to peremptory norms of general international law. Article 53 of the Vienna Convention on the Law of Treaties identifies two important features: the international community of States as a whole accepts and recognizes the norm as permitting no derogation, and modification requires a later norm of general international law with the same peremptory character. [1]
“No derogation” means that States cannot make an agreement setting the rule aside for their own relationship. Their consent does not make prohibited conduct lawful. A rule is not peremptory merely because it appears in an important treaty or because a commentator considers it morally compelling.
This also explains why jus cogens should not be treated as an ordinary additional item in the list of sources of international law. The inquiry concerns the special legal status of a norm, as well as the basis on which that norm exists.
What happens to a conflicting treaty?
Article 53 addresses a treaty that conflicts with an existing peremptory norm when it is concluded: the treaty is void. Article 64 addresses a different situation. If a new peremptory norm emerges, an existing treaty conflicting with it becomes void and terminates. The timing matters; an Article 64 case should not simply be described as invalidity from the treaty’s beginning.
Article 71 deals with consequences. In an Article 53 case, the parties must address the consequences of acts performed in reliance on conflicting provisions and bring their relations into conformity with the peremptory norm. Article 64 does not automatically erase every legal situation created before termination. [1]
Examples of jus cogens norms
The annex to the ILC’s 2022 draft conclusions lists norms the Commission has previously referred to as peremptory:
- the prohibition of aggression;
- the prohibition of genocide;
- the prohibition of crimes against humanity;
- the basic rules of international humanitarian law;
- the prohibition of racial discrimination and apartheid;
- the prohibition of slavery;
- the prohibition of torture; and
- the right of self-determination.
The list is expressly non-exhaustive. Its wording also matters: “the basic rules of international humanitarian law” should not be expanded into a claim that every provision of every humanitarian treaty is peremptory. [2]
What are erga omnes obligations?
An erga omnes obligation is owed to the international community as a whole. The expression is commonly translated as “towards all.” Its significance lies in the legal interest of all States in compliance, rather than only the interests of a State directly affected by a breach.
The leading explanation appears in Barcelona Traction, Light and Power Company, Limited (Belgium v. Spain), Second Phase, Judgment of 5 February 1970. In paragraphs 33–34, the ICJ distinguished obligations towards the international community as a whole from obligations arising towards another State in diplomatic protection. It identified aggression, genocide, and principles concerning basic human rights, including protection from slavery and racial discrimination, as examples. [4]
The case arose from Belgium’s attempt to protect Belgian shareholders in a company incorporated in Canada. The Court rejected Belgium’s claim to exercise diplomatic protection in the circumstances. Its explanation of erga omnes obligations therefore should not be recast as a judgment granting Belgium a general right to sue Spain on behalf of everyone.
What may a State claim when it is not itself injured?
Article 48 of the ILC State Responsibility Articles provides a framework for invocation by States other than an injured State. It covers obligations owed to the international community as a whole, as well as certain collective obligations owed to a group of States.
Under that framework, a qualifying State may seek cessation and, where appropriate, assurances of non-repetition. It may also claim performance of the obligation of reparation in the interests of the injured State or beneficiaries. This is different from claiming compensation for its own loss. The commentary identifies the latter provision on reparation as involving progressive development. [3]
The State Responsibility Articles are not themselves a treaty. Their provisions and commentaries must be assessed with attention to the relevant judicial decisions, State practice and the distinction between codification and progressive development.
Jus cogens vs erga omnes: comparison table
On a small screen, scroll the table horizontally.
| Question | Jus cogens | Erga omnes |
|---|---|---|
| What does it describe? | The peremptory status of a norm. | An obligation owed to the international community as a whole. |
| What is the main inquiry? | May States lawfully depart from the norm by agreement? | Which States have a legal interest in compliance? |
| What follows? | A conflicting treaty is subject to the rules on invalidity or termination. | States beyond the directly injured State may invoke responsibility under the applicable rules. |
| Which authorities are central? | VCLT Articles 53 and 64; the ILC’s 2022 conclusions. | Barcelona Traction, paragraphs 33–34; Article 48 of the State Responsibility Articles. |
| How do they relate? | Peremptory norms give rise to erga omnes obligations. | The classification does not by itself establish peremptory status. |
| Does it establish court jurisdiction? | No, not by itself. | No, not by itself. |
Are all jus cogens norms also erga omnes?
More precisely, jus cogens norms give rise to erga omnes obligations. Conclusion 17 of the ILC’s 2022 draft conclusions states this relationship. The commentary also explains that the reverse does not necessarily follow: not every erga omnes obligation arises from a peremptory norm. [2]
The distinction can be tested with two questions. First, does the obligation protect a community interest in which all States have a legal interest? Second, is the underlying norm accepted and recognized as permitting no derogation? An affirmative answer to the first question does not supply all the evidence needed for the second.
Calling an obligation erga omnes therefore does not, without further analysis, prove that a conflicting treaty is void. Equally, calling a norm jus cogens does not tell a claimant which court can hear a dispute about its breach.
Erga omnes and erga omnes partes: what is the difference?
Erga omnes refers to obligations owed to the international community as a whole. Erga omnes partes refers to obligations owed collectively to the parties within the relevant treaty regime. The common interest is shared by those parties.
Not every obligation in a multilateral treaty has this character. A treaty with many parties may still contain provisions governing reciprocal relations. The terms, purpose and relevant interpretation of the particular obligation must be examined.
Belgium v. Senegal: a practical illustration
In Questions relating to the Obligation to Prosecute or Extradite (Belgium v. Senegal), Judgment of 20 July 2012, the ICJ examined obligations under the Convention against Torture concerning Hissène Habré. Paragraphs 68–70 explain the common interest of treaty parties in compliance with the relevant obligations, including the preliminary inquiry and submission of the case to competent authorities for prosecution.
The Court held that Belgium, as a treaty party, could invoke Senegal’s responsibility without establishing a special interest. This was reasoning about erga omnes partes obligations. It did not mean that a shared interest alone established jurisdiction; the Court separately examined the Convention’s dispute-settlement provision. [5]
Why jurisdiction, immunity and enforcement still matter
Three separate questions often become confused: whether a rule was breached, whether a State may invoke responsibility, and whether a particular court may decide the claim. Jus cogens and erga omnes help answer the first two inquiries, but do not replace the rules governing the third.
Erga omnes does not remove the requirement of consent to ICJ jurisdiction
In East Timor (Portugal v. Australia), Judgment of 30 June 1995, Portugal challenged Australia’s conduct concerning a treaty with Indonesia. The ICJ accepted the erga omnes character of the right of self-determination. Nevertheless, it could not decide the dispute where doing so required determining the lawfulness of Indonesia’s conduct without Indonesia’s consent.
Paragraph 29 separates the character of the obligation from consent to jurisdiction. The decision shows why the importance of a right cannot cure every obstacle to adjudication. [6]
A State’s participation in the ICJ Statute also should not be confused with acceptance of jurisdiction over every dispute. The claimant needs an applicable jurisdictional basis and must satisfy its conditions.
Jus cogens does not automatically defeat State immunity in foreign civil proceedings
In Jurisdictional Immunities of the State (Germany v. Italy: Greece intervening), Judgment of 3 February 2012, the ICJ considered civil claims before Italian courts arising from acts committed during the Second World War. Italy argued that the peremptory character of the prohibitions involved displaced Germany’s immunity.
The majority rejected that argument. In paragraphs 92–97, it distinguished the substantive rules governing conduct from the procedural rules governing State immunity. Upholding immunity did not make the underlying acts lawful. [7]
The judgment must be read within its scope. State immunity in foreign civil litigation, the immunity of officials from foreign criminal jurisdiction, and proceedings before international criminal courts raise different questions. Judge Cançado Trindade’s contrary view was a dissent, not the majority holding.
A community interest does not authorize every response
Article 54 of the State Responsibility Articles preserves the position concerning lawful measures taken by qualifying States other than an injured State. It does not expressly establish a general entitlement to third-State countermeasures. The ILC’s commentary leaves that issue open to further development. [3]
An analysis of sanctions must identify the particular measure and the obligations it affects. A response that is independently lawful differs from a countermeasure that would otherwise breach an obligation. Neither “jus cogens” nor “erga omnes” supplies a general permission to use force or disregard other applicable law.
Three worked examples
The following situations are hypothetical. They illustrate the separate questions a lawyer must ask.
1. Two States agree to permit slavery
State A and State B conclude a treaty authorizing the enslavement of a group of people. Both governments say that they consented freely and expect economic benefits.
The relevant issue is whether their agreement conflicts with a peremptory norm. Assuming the Article 53 framework applies, the treaty is void because the prohibition of slavery cannot be set aside by agreement. Consent cannot validate the conflicting arrangement.
2. A distant State invokes responsibility for genocide
State C invokes State D’s responsibility for genocide committed against people within D’s own territory. C does not claim that its territory was attacked or its nationals were harmed.
The absence of that direct injury does not eliminate C’s legal interest in compliance with an erga omnes obligation. Whether C can pursue a particular judicial remedy still depends on jurisdiction, admissibility and the relevant rules on responsibility.
3. A claimant has a legal interest but lacks a forum
State C wishes to bring the same dispute before the ICJ, but cannot establish an applicable basis of jurisdiction. It argues that the gravity of genocide should be enough.
The argument confuses the importance of the substantive prohibition with the Court’s authority to decide the dispute. The prohibition remains binding, but the erga omnes interest does not itself supply the missing jurisdictional basis.
How to analyse a problem involving both concepts
Begin by identifying the precise obligation and its source. Then ask whether the underlying norm has peremptory status and whether the obligation is owed to the international community or collectively to treaty parties.
Next, identify the claimant’s legal interest, the proposed forum and the basis of its jurisdiction. Address immunity where relevant. Finally, examine the remedy or enforcement measure separately. This sequence avoids using the seriousness of the alleged wrong as a substitute for legal analysis.
For the wider framework of attribution, breach and reparation, see State Responsibility in International Law. For related judicial authorities, see 10 Landmark ICJ Cases.
Frequently asked questions
What is the main difference between jus cogens and erga omnes?
Jus cogens describes a norm’s peremptory status. Erga omnes describes an obligation owed to the international community as a whole. The first concerns whether departure by agreement is permitted; the second concerns the legal interest of all States in compliance.
Is genocide both jus cogens and erga omnes?
The prohibition of genocide is recognized as peremptory and gives rise to erga omnes obligations. Particular obligations under the Genocide Convention may also be owed collectively to its parties. The obligation being discussed should always be identified.
Can a State opt out of jus cogens by objecting?
The persistent-objector rule does not apply to peremptory norms, as stated in Conclusion 14(3) of the ILC’s 2022 draft conclusions. An individual State’s objection does not by itself create an exemption. [2]
Does erga omnes give individuals a right to sue before the ICJ?
No. Under Article 34(1) of the ICJ Statute, only States may be parties in cases before the Court. Individuals may have remedies under other legal systems, but erga omnes does not itself give them access to ICJ contentious proceedings. [8]
Is erga omnes the same as universal criminal jurisdiction?
No. Erga omnes concerns the community-wide character of an obligation. Universal criminal jurisdiction concerns the authority to prosecute particular crimes without the usual territorial or nationality connection. The applicable jurisdictional rules and any immunity must be examined separately; one label does not establish the other.
For examination answers: define each concept, explain their relationship, and illustrate the distinction with an authority. Then address jurisdiction separately. “All States have a legal interest” is not equivalent to “every court may hear the case.”
Primary authorities and further reading
- Vienna Convention on the Law of Treaties, 1969, Articles 53, 64 and 71.
- ILC, Draft conclusions on identification and legal consequences of peremptory norms of general international law (jus cogens), with commentaries, 2022, particularly Conclusions 2–7, 14, 17 and 23 and the annex. These conclusions are not a treaty.
- ILC, Articles on Responsibility of States for Internationally Wrongful Acts, with commentaries, 2001, particularly Articles 48 and 54. The Articles are not themselves a treaty; the commentary identifies elements of progressive development.
- Barcelona Traction, Light and Power Company, Limited (Belgium v. Spain), Second Phase, Judgment of 5 February 1970, I.C.J. Reports 1970, p. 3, paragraphs 33–34.
- Questions relating to the Obligation to Prosecute or Extradite (Belgium v. Senegal), Judgment of 20 July 2012, I.C.J. Reports 2012, p. 422, paragraphs 68–70; see also the separate examination of jurisdiction.
- East Timor (Portugal v. Australia), Judgment of 30 June 1995, I.C.J. Reports 1995, p. 90, paragraph 29.
- Jurisdictional Immunities of the State (Germany v. Italy: Greece intervening), Judgment of 3 February 2012, I.C.J. Reports 2012, p. 99, particularly paragraphs 91–97.
- Statute of the International Court of Justice, Articles 34 and 36.