Information powers of authorities and fundamental principles of law under the EU court’s microscope

My blogs in 2026 have examined cases where tax authorities’ requests for information, either for their own investigations or in connection with exchanges with other authorities, have been contested before courts:

“Foreseeably relevant” information or a “fishing expedition” in a transfer pricing case? June 22, 2026 , Privacy and tax information powers June 1, 2026 , Mutual Administrative Assistance in Tax Matters: Limits on Assistance January 21, 2026.

These cases have raised issues of fundamental importance that are not frequently aired in the courts. A recent decision of the EU General Court on the information gathering by the EU Commission for competition law purposes has raised very similar issues. While some issues are specific to competition law, others may have a direct relevance to information gathering and exchange by tax authorities. In particular, the court reviews important public law principles that are engaged.

In Vivendi SE v European Commission (Case T-1097/23) the Commission opened an investigation into the proposed acquisition by Vivendi SA of Lagardère SA, both large French-headquartered media companies. In furtherance of the investigation, the Commission sent the two companies requests for extensive information held in various communication means, received, sent or held by fifteen named individuals, as well as their successors and predecessors. Lengthy discussions between the companies and the Commission resulted in provision of certain information while other material was refused.

Purpose of the request

The court ruled that the Commission must state both the subject of its investigation and identify the competition rule allegedly infringed.  It need not carry out a rigorous legal characterisation of suspicions but must clearly indicates the suspicions it intends to investigate. The Commission may then request only information that enables it to do so. The purpose of the request must be indicated with sufficient precision and clarity, to determine whether the information is necessary and to enable the court to exercise its review powers.

Necessary information or fishing

The Commission may request all the information necessary for the performance of the tasks it undertakes as competition regulator (Article 11(1) of the Merger Regulation 139/2004). The companies argued that a request information which pursues an “exploratory purpose” is not “necessary” in this context.

The court upheld the Commission’s claim that the documents requested were essential to enable the Commission to analyse whether Vivendi’s intervention, consultation, and/or association with, certain decisions taken by Lagardère could be characterized as an exercise of decisive influence by Vivendi. The necessity of information requested is to be determined by reference to the purpose stated in the request: in other words, the suspicions of an infringement that the Commission intends to investigate. The connection between the information requested and the suspected infringement is met if the Commission can reasonably assume, at the time of the request, that the information is likely to help it determine whether that infringement has occurred.

Scope of the request

The companies also argued that reasons were not given for the particular documents or  search terms they were required to apply. The Court however said that the Commission cannot be required, before any request for information, to know the content of the documents requested or their relative importance for the purposes of the investigation. It was not necessary for the Commission to provide specific reasons why each item of information or search term requested was necessary or would contain information relevant to a preliminary enquiry.

The stage of the investigation and whether or not the Commission already possesses information on the alleged infringements must be taken into account in assessing the scope of the obligation to provide reasons.

The applicant’s arguments challenging the necessity of the requested information were held to relate to the substantive legality of the contested decision and could not be taken into account in assessing the obligation to provide reasons: the obligation to provide reasons must be distinguished from the merits of the contested act.

Misuse of power

A misuse of power in EU law is the use of a power by an administrative authority for a purpose other than that for which it is conferred. Such a misuse can only be established on the basis of objective, relevant, and consistent evidence.

The court rejected the companies’ arguments that the information could not be for the purpose of assessing the compatibility of a merger with the internal market. They argued that the merger had been authorised by the Commission three months before the investigation was formally commenced and so the request was therefore aimed at another purpose, which was subject to more rigorous safeguards than the authority for the procedure in question.  The court decided that it is for the Commission to assess whether information is necessary to detect an infringement of competition rules.

Arbitrary or disproportionate intervention by a public authority

The prohibition of arbitrary or disproportionate interventions by public authorities in the private sphere of a person, whether natural or legal, is a general principle of EU law.  In the competition law context, the information request must aim to gather the documentation necessary to verify the reality and scope of specific factual and legal situations, about which the Commission already has information, constituting sufficiently serious indications of an infringement of competition rules. The companies argued that, at the time of requiring the information, the Commission did not have sufficiently serious evidence to suspect an infringement and the information it held should be disclosed.

Right to a defence

The right to a defence in the conduct of administrative proceedings in competition matters is also a general principle of EU law.

The administrative procedure in question was divided into two distinct and successive stages: a preliminary investigation phase and an adversarial stage.  Full access to the right to a defence apply at the adversarial stage when, the company can access  the Commission’s information to enable it to  exercise  that rights. The investigative stage also inherently implies an accusation of infringement which means that defence rights must also not be irreparably compromised during this stage.  The court decided that the Commission may only request information that enables it to verify the presumptions of infringement justifying the investigation and that are indicated in the request for information.

The companies argued that the information available to the Commission appeared to have been submitted by third parties, including Reporters Without Borders (RWB). This evidence, they said, did not establish a presumption of wrongdoing because it was slanderous and of dubious origin due to “RWB’s well-known and long-standing hostility” towards  the companies. The court concluded that the companies did not explained the reasons why the origin of the documents, would undermine the legality of the request and the Commission had recognised RWB as an interested third person under Article 18(4) of Regulation No 139/2004.

“impossibilium nulla obligatio est”

The principle that “no one is bound to do the impossible” is a general principle of EU law. Such an impossibility requires first, the reality of the difficulties invoked and, second, the absence of alternative means of implementation.

The companies argued that from the outset, it was objectively and absolutely impossible to obtain documents from one of its shareholders over which it has no control. The court found that there was no evidence to suggest that such an impossibility existed at the time the documents were demanded by the Commission and  Vivendi had already provided documents originating from the shareholder’s group, indicating that it was able to comply.

Proportionality

Proportionality, one of the general principles of EU law, requires that the acts of EU institutions must not exceed the limits of what is appropriate and necessary to achieve the legitimate objectives pursued by the legislation in question. Where a choice exists between several appropriate measures, the least restrictive should be used and that the disadvantages caused must not be disproportionate to the aims pursued. Thus, the obligation to provide information must not be disproportionate in relation to the needs of the investigation.

The fact that a significant workload is imposed was held not itself sufficient to be disproportionate. The court decided that the Commission cannot be required to know the content or importance of the documents in advance and that the requested documents did not go beyond what was necessary for the investigation.

Relevance

The companies argued that (a) the choice of nearly four years was arbitrary, given that no particular relevant event occurred then (b) the designation of fifteen individuals including some who had no connection whatsoever with Lagardère or the merger was motivated by irrelevant considerations (c) “tens of thousands of documents” without search terms was disproportionate.

The court rejected all three contentions on the basis of evidence that information over that period would help determine whether an infringement had occurred, it was reasonable to assume that prominent executives would have involvement in the alleged infringements and  the alleged  motivation was unsubstantiated, and further that of “several hundred thousand documents” had already been provided.

Human rights and choice of search terms

The companies argued that the requirement  to apply about one hundred search terms to all the professional and/or personal communication tools of the persons concerned (a)  without any clarification as to how these terms were selected or specifically justified, (b) specifying the date range, without relating them to the subject of the  investigation, was likely to reveal personal information concerning the political or religious beliefs of the individuals, and as well as the identity or content of exchanges with journalistic sources. This the argued violated the privacy of the individuals concerned and the protection of journalistic sources contrary to Articles 7 and 11 of the EU Charter of Rights and Articles 8 and 10 of the European Convention on Human Rights.

Journalistic sources

The court ruled that EU law provides a complete system of legal remedies for effective judicial protection, which respects all the procedural safeguards concerning the protection of journalistic sources which enables a judge to review material before it is provided to the Commission to determine whether any communication is privileged. That requires a separate procedure which the applicant must invoke. Further, it considered that the companies did not have standing to raise these issues for the individuals and noted that the Commission had offered a procedure to deal with privileged material.

Privacy

The right to privacy was similarly not infringed as the information was for a lawful purpose and interference with the right not disproportionate. The information would also be subject to strict security and data protection controls.

Concluding observations

The companies failed to prevent disclosure of the information on all grounds. This failure does not imply that in appropriate cases, a taxpayer could not succeed with any of these public law principles in relation to a tax authority demand for information.

Where information is requested or exchanged pursuant to the EU Mutual Assistance Directive 2011/16 or the Mutual Assistance in the Recovery of Taxes Directive 2010/24, the full range of  EU rights including the Charter of Rights are engaged. In the case of  exchange of information exchanged by treaty, the European Convention on Human Rights will apply to exchanges among the 46 Council of Europe members states. Other international human rights conventions will similarly apply such as the African Charter on Human and People's Rights to treaties with its 54 parties. Article 31(c) of the Vienna Convention on the law of treaties makes in clear that such instruments must be taken into account in construing the exchange of information provisions of tax treaties.

To the extent that the public law principles set out in the Vivendi decision also reflect national public law principles, they will likewise apply in these cases.