Rule of Double Criminality

The Rule of Double Criminality is a fundamental principle of extradition under which the conduct for which extradition is sought must generally constitute a criminal offence under the laws of both the requesting State and the requested State. The rule protects State sovereignty and prevents a person from being extradited for conduct that is not recognised as criminal by the requested State.

Meaning

Double criminality means that the same underlying conduct must be criminal in both States.

For example:

Person commits conduct in State A

↓

State A → treats conduct as a crime

State B → also treats the same conduct as a crime

↓

Double criminality satisfied

The requirement does not necessarily mean that the offence must have the same name or identical legal definition in both States.

Purpose of the Rule

The rule serves several purposes:

• protects the sovereignty of the requested State;
• prevents extradition for conduct that is not criminal in that State;
• protects individual liberty;
• promotes fairness in international criminal cooperation;
• prevents States from using extradition to enforce their criminal laws beyond accepted limits.

Basic Requirements

For double criminality to be satisfied, the following elements are generally relevant:

1. There must be identifiable criminal conduct.
2. That conduct must constitute an offence under the law of the requesting State.
3. The same conduct must constitute an offence under the law of the requested State.
4. The applicable extradition treaty or domestic law must permit extradition for that offence.

Same Conduct Test

Modern extradition arrangements often focus on the conduct underlying the offence, rather than requiring identical legal classifications.

For example:

State A → calls conduct “Fraud”

State B → calls substantially the same conduct “Deception”

If the underlying conduct is criminal in both States, double criminality may be satisfied.

Thus:

Same conduct is more important than identical terminology.

Identical Offence Not Required

The offence does not necessarily have to be:

• described by the same name;
• located in the same section of criminal legislation;
• defined using identical words;
• punished in exactly the same manner.

The important question is generally whether the essential conduct is criminal in both jurisdictions.

Example

Suppose a person is accused in State A of obtaining money through deliberate deception.

State A describes the offence as:

Fraud

State B does not use the word “fraud” but criminalises:

Obtaining property by deception

If the conduct alleged against the person falls within State B’s offence, the requirement of double criminality may be satisfied.

Extradition Treaty

The precise operation of double criminality depends upon the applicable:

• extradition treaty;
• domestic legislation;
• multilateral convention;
• other applicable legal arrangement.

Some treaties use a list approach, while modern treaties frequently use a threshold approach based on the seriousness of the offence.

List Approach

Under the traditional list approach, the extradition treaty specifies offences for which extradition may be granted.

For example, the treaty may list:

• murder;
• robbery;
• kidnapping;
• fraud;
• terrorism.

The requested State examines whether the alleged conduct falls within an extraditable offence on the list.

Threshold Approach

Modern extradition treaties may instead use a minimum punishment threshold.

For example:

Offence punishable by at least X years’ imprisonment

↓

May qualify as an extraditable offence

This approach avoids the need to constantly update a treaty whenever States change the names or classifications of offences.

Difference in Punishment

The punishment for the same conduct does not necessarily have to be identical in both States.

For example:

State A → maximum punishment: 10 years

State B → maximum punishment: 5 years

The difference in punishment alone does not necessarily defeat double criminality.

The key issue is whether the underlying conduct is criminal in both jurisdictions, subject to the applicable treaty requirements.

Difference in Legal Classification

Different legal classifications do not necessarily defeat extradition.

For example:

State A → “embezzlement”

State B → “misappropriation”

If the essential conduct is criminal in both States, double criminality may be satisfied.

Difference in Terminology

International criminal cooperation would become difficult if extradition required identical terminology.

Therefore, modern extradition law generally focuses on the substance of the conduct, rather than merely its legal label.

Partial Correspondence

The requested State does not necessarily need to find an offence that is word-for-word identical.

It must generally determine whether the alleged conduct would constitute an offence under its own law.

Thus:

Conduct in request

↓

Compare with law of requested State

↓

Would this conduct constitute an offence?

↓

Yes → double criminality may be satisfied

Time of Assessment

The relevant law of the States and the applicable treaty determine how the double-criminality requirement is assessed.

A particularly important question can arise where the conduct was criminal in one State but was not criminal in the requested State at the relevant time.

The precise answer depends upon the applicable extradition framework.

Retrospective Criminalisation

Double criminality also protects against extradition for conduct that was not criminal under the applicable law at the relevant time.

This is connected with the broader principle of nullum crimen sine lege:

No crime without law.

A person should not ordinarily be extradited for conduct that was not criminal when it occurred, subject to the applicable international and domestic legal framework.

Dual Criminality and Human Rights

The rule also provides a measure of protection for individuals.

A person should not ordinarily be surrendered to another State for conduct that the requested State itself does not recognise as criminal.

However, satisfaction of double criminality does not automatically require extradition.

Other grounds of refusal may still apply, including:

• torture risk;
• political persecution;
• death penalty concerns;
• double jeopardy;
• speciality;
• other treaty-based grounds.

Double Criminality vs Speciality

These two principles are frequently confused.

Double Criminality

Asks:

Is the conduct criminal in both States?

Speciality

Asks:

For what offence may the person be prosecuted after extradition?

Therefore:

Double criminality → before surrender

Speciality → controls prosecution after surrender

Double Criminality vs Political Offence Exception

These are also distinct.

Double criminality → whether the conduct is criminal in both States

Political offence exception → whether extradition should be refused because of the political character of the offence

An extradition request can satisfy double criminality but still be refused on another ground.

Double Criminality and Nationality

The nationality of the accused is generally separate from the double-criminality requirement.

A person may be extraditable regardless of nationality where the applicable law permits it.

Some States, however, separately prohibit or restrict extradition of their nationals.

Double Criminality and Universal Jurisdiction

Universal jurisdiction can complicate extradition where a State claims jurisdiction over an offence regardless of where it occurred or the nationality of the offender.

The requested State must still apply the relevant extradition treaty and domestic law.

Double Criminality and International Crimes

For serious international crimes, treaties and domestic legislation may establish specific extradition obligations.

These may concern:

• genocide;
• war crimes;
• torture;
• terrorism;
• transnational organised crime.

The relevant treaty may modify or specify how double criminality operates.

Importance in International Cooperation

The rule creates a common legal foundation for extradition.

It prevents a situation where:

State A → criminalises conduct

↓

State B → does not criminalise conduct

↓

State A demands surrender

↓

State B → may refuse because conduct is not criminal under its law

This respects the independent criminal-law choices of States.

Common Confusions

Does the offence need exactly the same name in both States?

No.

Must the punishment be identical?

No. The precise treaty may impose additional requirements, but identical punishment is generally not necessary.

Must the criminal statutes use identical wording?

No.

What must generally be the same?

The underlying criminal conduct must generally be criminal in both States.

Does satisfying double criminality guarantee extradition?

No. Other grounds for refusal may apply.

Is double criminality the same as speciality?

No.

Double criminality → criminal in both States

Speciality → limits subsequent prosecution

Is double criminality required in every extradition case?

Its application depends upon the applicable treaty and domestic legal framework, although it is a widely recognised principle of extradition.

Topic at a Glance

Point Position Meaning Conduct must generally be criminal in both States Main context Extradition Focus Underlying conduct Identical offence name Not required Identical legal definition Not required Identical punishment Not generally required Main purpose Protect sovereignty and individual liberty List approach Treaty specifies offences Threshold approach Treaty uses minimum punishment Speciality Separate principle Political offence Separate ground of refusal Human rights May independently restrict extradition Key idea Same criminal conduct, not necessarily same terminology

Quick Revision

• Double criminality is a fundamental principle of extradition.
• The alleged conduct must generally be criminal under the laws of both States.
• The offence does not have to have:
  • the same name;
  • identical wording;
  • identical legal classification.
• The focus is generally on the underlying conduct.
• Different punishments do not automatically defeat double criminality.
• The rule protects:
  • State sovereignty;
  • individual liberty;
  • fairness in extradition.
• Extradition treaties may use:
  • list approach;
  • threshold approach.
• Double criminality is different from speciality.
• Satisfaction of double criminality does not automatically mean extradition must be granted.
• Other grounds of refusal may still apply.
• The essential principle is:

A person should generally be extradited only where the conduct for which surrender is sought constitutes a criminal offence in both the requesting State and the requested State.

Conclusion

The Rule of Double Criminality is a fundamental principle governing extradition and requires that the conduct underlying an extradition request generally constitute a criminal offence in both the requesting State and the requested State. Its purpose is to protect territorial sovereignty, prevent the surrender of persons for conduct that is not criminal in the requested State, and provide an important safeguard for individual liberty. Modern extradition law generally focuses on the substance of the conduct rather than identical legal terminology. Consequently, the same offence need not have the same name, statutory definition or punishment in both jurisdictions. Extradition treaties may adopt either a traditional list approach identifying extraditable offences or a modern threshold approach based on the seriousness of the applicable punishment. Double criminality must also be distinguished from the rule of speciality, which limits prosecution after extradition. Even where double criminality is satisfied, extradition may still be refused on grounds such as human-rights concerns, political persecution, torture, death penalty or double jeopardy. Thus, the rule represents an important balance between international cooperation in criminal justice and respect for the sovereign criminal-law systems of individual States.