To verify case law cited by an AI, you identify the court and the decision's identifier (numéro de pourvoi or appeal number, numéro RG or docket number, ECLI), look it up in the official database that publishes it, then check that the number, the date and the quoted passage match. A reference that fails this check is not cited.
A generative AI can produce a credible reference for a decision that does not exist: this is what is called a hallucination, covered in detail in our article on the reliability of ChatGPT for law. French courts now point them out in written submissions.
The administrative court of Orléans thus noted, in a judgment of 29 December 2025 (no. 2506461), fifteen non-existent case-law references in a lawyer's submissions: either no decision existed with the number given, or the numbers did not match the dates attached to them. The court invited counsel to check that the references were not the result of a "hallucination".
Responsibility remains the lawyer's. The Règlement intérieur national (RIN, the national code of conduct of the French bar), in its article 1.3, requires lawyers to show competence, dedication, diligence and prudence towards their clients. The practical guide of the Conseil national des barreaux (CNB, France's national bar council) on the use of generative AI systems (September 2024) recommends always verifying the accuracy of the content produced.
Each branch of the court system has its own numbering system. Recognising the form of the identifier tells you where to look, and lets you spot a malformed reference before you even start searching.
| Court | Identifier | Example of the form |
|---|---|---|
| Cour de cassation | Numéro de pourvoi (appeal number) | 17-14.499 |
| Court of appeal | Number of entry in the répertoire général (RG) | RG 25/03153 |
| Conseil d'État, administrative courts of appeal, administrative courts | Application number | 2506461 |
| Cour de cassation, Conseil d'État, among others | ECLI | ECLI:FR:CCASS:2013:CR00710 |
The numéro de pourvoi (appeal number) of the Cour de cassation (France's supreme civil court) is made up of two digits, a hyphen, then five digits with a full stop after the first two. A reference such as "Cass. civ. 2e, 29 mars 2018, n° 17-14.499" thus gives three elements to cross-check: the chamber, the date and the number.
For the courts of appeal, the court registry keeps a general register (répertoire général) of the cases brought before the court, which records in particular the entry number (article 726 of the Code of Civil Procedure). This numéro RG (répertoire général, docket number) appears on the judgment, for example in the form "N° RG 25/03153".
The ECLI (European Case Law Identifier) is a common European identifier, based on conclusions of the Council of the European Union published in 2011. It has five elements separated by colons: the ECLI prefix, the country code, the court code, the year of the decision and a serial number. For the Cour de cassation, the court code is always CCASS. For the Conseil d'État (France's highest administrative court), several codes exist (CESSR, CECHR, CEASS, among others), the code CE on its own not being used.
The database to consult depends on the court and the date of the decision. Court decisions are made available as open data on a timetable set by the order of 28 April 2021, amended since, court by court.
Judicial courts: Judilibre. Since 1 October 2021, the search engine of the Cour de cassation (Judilibre) has published the decisions the Court delivers in public, as well as the judgments of the courts of appeal delivered in open court in civil, employment and commercial matters from 15 April 2022 (Cour de cassation, open data and API). The timetable then provided for the commercial courts on 31 December 2024, the tribunaux judiciaires (first-instance civil courts) on 30 September 2025 and the conseils de prud'hommes (France's labour courts) on 30 September 2026.
Administrative courts: the open data portal of the administrative courts. It publishes the decisions of the Conseil d'État since 30 September 2021, of the administrative courts of appeal since 31 March 2022 and of the administrative courts since 30 June 2022. ArianeWeb, the Conseil d'État's database, for its part brings together decisions of the Conseil d'État and of the administrative courts of appeal (Conseil d'État, open data).
Légifrance. The official French legal information website publishes the case law of the Cour de cassation in two databases, CASS for judgments "Publié au Bulletin" (published in the official Bulletin) and INCA for unpublished judgments since 1989, and only a selection of judgments of the courts of appeal.
Finding a number is not enough. The Orléans judgment shows it: for some of the faulty references, the number did not match the date attached to it. The check therefore covers each element of the reference:
The level of publication then helps weigh the authority of the judgment. The Judilibre engine lets you filter judgments "Publié au Bulletin", "Publié au Rapport" and "Publié aux Lettres de chambre". According to the Cour de cassation, published judgments represent approximately 10% of its decisions, and those published in the Rapport carry an even stronger doctrinal weight (Bulletins of judgments). An unpublished judgment cited as a leading case should raise a flag.
A reference that cannot be found is not necessarily invented. Database coverage is partial: Judilibre only publishes court of appeal judgments from April 2022, and Légifrance publishes only a selection of them. An older decision may exist without being online.
The rule remains simple: a reference that cannot be verified against the text of the decision is not cited. If it is essential, you need to obtain the decision itself from the court or from the party relying on it. Asking a general-purpose AI to "confirm" its own reference does not count as verification: only reading the decision does.
Verification costs less when the tool starts from real decisions rather than from its memory. A tool that works on a base of identified decisions links each result to a decision you can open and reread. On the criteria to examine before equipping yourself, see which legal AI to choose by use and, for the European framework, what the AI Act changes for lawyers.
Plato, the only AI specialised in personal injury, is built on this principle: every amount is tied to real decisions from its base of more than 84,000 quantified decisions, and stays traceable back to the decision it comes from. The method for finding these decisions is set out in how to find quantified case law in personal injury. The final verification remains the lawyer's.
What is an ECLI?
It is the European Case Law Identifier. It has five elements separated by colons: ECLI, the country code, the court code, the year of the decision and a serial number. For the Cour de cassation, the court code is always CCASS.
What does a Cour de cassation appeal number look like?
Two digits, a hyphen, then five digits with a full stop after the first two, for example 17-14.499. Together with the chamber and the date, it is one of the three elements to cross-check.
Where do you verify a court of appeal judgment?
On Judilibre, which publishes the judgments of the courts of appeal delivered in open court in civil, employment and commercial matters from 15 April 2022. Légifrance publishes only a selection of them.
Is a decision that cannot be found necessarily invented?
No. The official databases do not cover every decision, in particular court of appeal judgments prior to April 2022. But a reference that cannot be verified against the text of the decision is not cited.
What does "publié au Bulletin" mean?
It is one of the publication levels of Cour de cassation judgments, alongside publication in the Rapport and in the Lettres de chambre. Published judgments represent about 10% of the Court's decisions, according to the Court.
Are administrative court decisions available as open data?
Yes, since 30 June 2022, on the open data portal of the administrative courts, which also publishes the decisions of the Conseil d'État since 30 September 2021 and of the administrative courts of appeal since 31 March 2022.