Judicial Interpretation Of European Investigation Orders

06 Nov 2025 --
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Judicial Interpretation of European Investigation Orders (EIOs)

The European Investigation Order (EIO) is an EU mutual-recognition instrument enabling one Member State (“the issuing state”) to request investigative measures to be carried out in another Member State (“the executing state”). Judicial interpretation by the Court of Justice of the European Union (CJEU) focuses heavily on:

Key Principles Interpreted by Courts

Mutual Recognition & Trust
The default principle is that executing authorities must comply unless a refusal ground applies. However, trust is not blind: the CJEU has emphasized effective judicial protection.

Proportionality
The issuing state must ensure that the measure is necessary and proportionate. Courts assess whether less intrusive measures were possible.

Judicial Authorization
If a measure interferes with fundamental rights (searches, telecommunications data, surveillance), judicial involvement is required at issuance or execution, depending on national law.

Fundamental Rights & Charter Compliance
Especially Articles 7, 8, 47, 48 of the EU Charter (privacy, data protection, fair trial, defence rights).

Grounds for Refusal
Limited and exhaustively listed, but courts have interpreted how strictly they apply (e.g., immunity, privileges, rights breaches).

Remedies and Challenges
The CJEU emphasizes that persons affected by an EIO must have access to effective remedies in either the issuing or executing state.

CJEU Case Law on the European Investigation Order

Below are four major CJEU cases that directly concern EIOs.
Each is explained clearly and in detail.

1. C-324/17 – Gavanozov I (2019)

Topic: Availability of a legal remedy against the issuance of an EIO

Background

A Bulgarian court issued an EIO for investigative measures in another Member State. Bulgarian law did not provide any legal remedy for the suspect to challenge the issuance of an EIO. A Bulgarian court therefore asked the CJEU whether such lack of a remedy violates EU law.

CJEU’s Key Findings

Effective Remedies Required
The Court held that persons affected—especially suspects—must have the ability to challenge the legality of investigative measures at some point in the process.

Remedy Must Exist Either in the Issuing State or Executing State

The issuing state cannot avoid judicial review by arguing that challenges may be possible later in the executing state.

There must be a clear, accessible remedy.

Fundamental Rights Protection
The CJEU emphasized the need to safeguard:

Article 47 (effective judicial protection),

Article 48 (rights of defence),
of the Charter of Fundamental Rights.

Impact

GAVANOZOV I forced several Member States to amend legislation to guarantee judicial review of orders that could deeply affect rights.

2. C-852/19 – Gavanozov II (2021)

Topic: Can an executing state refuse to execute an EIO if the issuing state lacks remedies?

Background

The Bulgarian law still did not provide a judicial remedy after the Gavanozov I judgment. The executing authority asked whether it could refuse to carry out the EIO because the issuing country violates fundamental-rights requirements.

CJEU’s Key Findings

Yes – In Exceptional Circumstances Execution May Be Refused
An executing authority may refuse to execute an EIO where systemic or generalised deficiencies in the issuing state cast real doubt on fundamental rights.

Not Automatic Refusal
The executing judge must:

assess evidence of systemic problems,

check whether these deficiencies concretely affect the person concerned,

seek further information from the issuing state.

Mutual Trust is Not Absolute
The ruling emphasized that mutual trust must be balanced with rights protection under the Charter.

Impact

GAVANOZOV II created a “two-step test” similar to the one used for the European Arrest Warrant (LM / Celmer test), adapting it to EIO execution.

3. C-66/20 – X (2021)

Topic: Judicial authority and proportionality for freezing and evidence-gathering measures

Background

The case concerned whether a prosecutor in the issuing state qualified as a sufficiently independent “judicial authority” to issue an EIO involving intrusive measures (search, seizure, financial data).

CJEU’s Key Findings

Prosecutors May Issue EIOs — But Must Be Independently Acting
A prosecutor can issue an EIO if:

they operate independently from the executive,

their actions are subject to judicial oversight or review.

Strict Proportionality Requirement
For intrusive measures (search, seizure, freezing):

The EIO must contain specific reasoning regarding necessity.

Measures must not be overly broad or speculative.

Execution State May Review Proportionality
Although primary responsibility lies with the issuing authority, the executing authority may review proportionality where fundamental rights are at risk.

Impact

This judgment clarified the status of prosecutors as issuing authorities and strengthened procedural safeguards for intrusive investigative acts.

4. C-746/18 – H.K. (2021)

(While not exclusively about EIOs, the Court’s ruling has been repeatedly applied by national courts to EIO cases because it concerns the judicial authorization required for access to communications data, a frequent investigative measure requested via EIOs.)

Topic: Access to telecommunications and metadata – need for judicial review

Background

Authorities had obtained access to telephone data without prior judicial authorization. The question was whether such access was compatible with the Charter (Articles 7, 8, 11, 47).