Between 2023 and 2026, France’s Supreme Court, the Cour de cassation, developed a proportionality test that now governs many business evidence disputes.
Evidence protected by trade secret rules may sometimes be produced in court.
Even unlawfully or unfairly obtained evidence is not automatically excluded.
However, the evidence must be indispensable to the claim and the interference with competing rights must remain strictly proportionate.
A January 28, 2026 ruling marks the practical boundary: evidence obtained from former employees’ personal messaging accounts was excluded because the intrusion into privacy and secrecy of correspondence was disproportionate.
For companies operating in France, the rule is therefore:
The right to evidence can go far, but it does not create a license to investigate by any means available.
How Does France Define a Trade Secret?
French trade secret protection is governed by Articles L. 151-1 et seq. of the French Commercial Code, which implemented EU Directive 2016/943.
The regime is separate from traditional intellectual property rights such as patents, trademarks, and copyright.
Under Article L. 151-1, information qualifies for protection only if three cumulative conditions are satisfied:
- it is not generally known or readily accessible to people familiar with the relevant industry;
- it has actual or potential commercial value because it is secret;
- the lawful holder has taken reasonable steps to keep it secret.
That third condition matters operationally.
Calling a document “confidential” is helpful, but it does not necessarily make it a legally protected trade secret.
Companies should be able to show concrete protective measures such as:
- access restrictions;
- confidentiality legends;
- need-to-know policies;
- IT permissions;
- employee confidentiality obligations;
- and documented exit procedures.
In a February 5, 2025 decision involving Domino’s Pizza, the Cour de cassation considered the restricted distribution of an internal guide and confidentiality notices appearing on each page when assessing trade secret protection.
2023: French Courts Will Not Authorize a Fishing Expedition
The first important step came in Cour de cassation, Commercial Chamber, November 8, 2023, No. 22-13.149.
The Court held that a party cannot be ordered to produce evidence where the existence of that evidence and its possession by that party are not at least plausible.
For U.S. readers, this is important because French civil procedure does not provide the broad discovery system familiar in U.S. litigation.
A claimant cannot simply seek wide access to an opponent’s files in the hope of finding something useful.
There must first be a sufficiently concrete evidentiary basis.
2024: Trade Secret Protection Can Yield to the Right to Evidence
In Cour de cassation, Commercial Chamber, June 5, 2024, No. 23-10.954, the Court clarified that trade secret protection is not absolute.
Evidence covered by a trade secret may be produced when:
- the evidence is indispensable to the exercise of the right to evidence;
- and the interference with trade secret protection is strictly proportionate to the objective pursued.
The rule relies in part on Article L. 151-8 of the French Commercial Code and Article 6(1) of the European Convention on Human Rights.
The practical implication is significant.
A company cannot invoke trade secret protection simply to prevent the opposing party from proving a legitimate claim.
French courts must balance the competing interests.
2025: Unlawfully Obtained Evidence Is Not Automatically Excluded
The Court moved one step further in Cour de cassation, Commercial Chamber, February 12, 2025, No. 23-18.415.
It held that unlawfulness or unfairness in obtaining or producing evidence does not automatically require exclusion in a civil case.
Instead, the judge must evaluate the fairness of the proceedings as a whole and balance:
- the right to evidence;
- the competing rights affected;
- whether the evidence is indispensable;
- and whether the interference is strictly proportionate.
This does not mean French courts freely admit improperly obtained evidence.
In that case, the challenged evidence was ultimately excluded because of the unfair circumstances in which it had been created.
The same principle was reaffirmed on September 17, 2025, No. 24-14.689, in a case involving a private investigator who concealed his true status.
The Cour de cassation held that the evidence could not simply be excluded because of the deceptive method used. The proportionality analysis still had to be performed.
2026: Personal Privacy Becomes the Clear Boundary
The limits of this increasingly flexible approach became visible in Cour de cassation, Commercial Chamber, January 28, 2026, No. 24-13.062.
The dispute involved evidence collected from former employees’ personal messaging accounts.
The Cour de cassation upheld its exclusion because the methods used created a disproportionate interference with privacy and the secrecy of correspondence.
That ruling provides a useful practical boundary.
A company may have a legitimate interest in proving trade secret theft or unfair competition.
That interest does not automatically justify accessing private communications.
The seriousness of the suspected misconduct does not eliminate the proportionality requirement.
How Can a Company Secure Evidence Legally in France?
For U.S. executives and counsel, one of the most important differences is procedural.
France does not have broad U.S.-style pretrial discovery.
Instead, Article 145 of the French Code of Civil Procedure provides a targeted pre-litigation evidence mechanism.
Where there is a legitimate reason to preserve or establish evidence before litigation, a French court may order legally permissible investigative measures.
Depending on the circumstances, the request may be brought:
- in adversarial summary proceedings;
- or through an ex parte application where the applicable requirements are satisfied.
For suspected trade secret misappropriation, this procedure can be strategically important.
It may allow the company to secure evidence through a judicially supervised process instead of taking the much greater risk of searching personal devices or accounts on its own.
French law also provides mechanisms to protect trade secrets discovered during these measures, including temporary escrow and restricted disclosure procedures.
Are Stronger Employee Confidentiality Clauses the Answer?
They are part of the answer, but not the entire solution.
Companies with employees or executives in France should review:
- confidentiality clauses;
- IT policies;
- access rights;
- data classification;
- offboarding procedures;
- return and deletion obligations;
- and litigation hold or evidence-preservation processes.
The purpose is twofold.
First, the company must demonstrate that it actually treated the information as secret.
Second, it must preserve evidence of any future misuse without creating a second legal problem through an unlawful investigation.
An extremely broad confidentiality clause cannot compensate for poor internal protection.
So How Far Can a Company Go?
French case law from 2023 through 2026 now provides a relatively coherent answer.
The right to evidence may justify using information protected as a trade secret and, in exceptional cases, even evidence obtained unlawfully or unfairly.
However, the evidence must be indispensable, and the interference with competing rights must be strictly proportionate.
The line is crossed when evidence collection becomes an excessive intrusion into fundamental rights such as privacy or secrecy of correspondence.
That distinction changes the practical question for management.
The objective is not simply to obtain evidence.
The objective is to obtain evidence that a French court can actually use.
Why This Is a Governance Issue
Trade secret protection should therefore be designed before a suspected leak occurs.
Legal, HR, IT, cybersecurity, and management teams should determine in advance:
- which information qualifies as sensitive;
- who may access it;
- how access is logged;
- what happens when an employee leaves;
- how suspected leakage is escalated;
- and when external counsel or an Article 145 application should be considered.
For companies operating in France, an effective legal function protects two separate assets:
the trade secret itself and the future admissibility of the evidence needed to enforce it.
That is the real lesson of the Cour de cassation’s 2023-2026 case law.