What is case law? Understanding the notion of "jurisprudence" under French law

In the French legal landscape, case law — the way in which a court usually judges an issue — occupies a place that is both essential... and complex. Neither a real source of law in the strict sense, nor a simple interpretation of laws, it is as intriguing as much for law students as for litigators.

So What exactly is the case law ? And above all, What is its value under French law ?

The nature and value of case law in French law

Contrary to popular belief, case law is not a formal source of law in France, at least not to the same extent as the law or regulations. In fact, l'article 5 of the Civil Code prohibits judges from making decisions by way of general and regulatory provisions.

In other words, a judge cannot create a general rule of law.

This power belongs, in a simplified manner, to Parliament alone, in accordance with articles 24 and 34 of the Constitution.

However, the judge cannot be the sole source of the law. As such, article 6 of the Civil Code prohibits him from refusing to judge.” under the pretext of silence, darkness or the inadequacy of the law ”, otherwise he would be guilty of a denial of justice.

It follows from these two injunctions that, while the judge can and must interpret the law, he can only do so in connection with a particular dispute.

It is therefore the repetition of a similar interpretation by judges in similar situations that gives rise to consistent case law.

However, as the Court of Cassation often recalls, since this interpretation is purely circumstantial, no one can rely on an acquired right to fixed case-law (Cass. Civ. 1^re, November 12, 2020, n° 19-16.964).

In theory, therefore, the judge does not create law; he discovers and rediscovers it during each litigation.

The necessary corollary of this fiction is simple: even in the presence of consistent case law, if the judge adopts a new interpretation of the law during the trial, it applies immediately. Why? Because the law, as interpreted in this way, is deemed to have always existed at the time of the facts.

We are talking about immediate application to ongoing proceedings.

The move towards a necessary modulation of the effect of case law over time

Therefore, logically, no one can rely on consistent case law.

However, in practice, all legal professionals — lawyers, notaries, corporate lawyers and magistrates — refer daily to existing case law to make their decisions.

Lawyers thus advise their client and build their strategy based on the law applicable at the time they are interviewed. Depending on the law, of course, but also (and especially) in terms of case law.

There is therefore a real danger that the said client will be, during his trial, the “victim” of a reversal of case law.

This situation creates a real risk of legal uncertainty and a violation of the right to a fair trial, which has prompted some academics to think about” the opportunity to establish, in our legal system, a transitional law of changes in case law ” (Nicolas Molfessis, The Reversal of Jurisprudence, Litec, 2005).

While the proposal is attractive in practice, it is nevertheless, for those most committed to theory, it is nothing less than” technically indefensible ”,” gravely ignorant of the constitutional principle of the separation of powers and constitutes an unacceptable provocation to a rebellion against the rule of law (Vincent Heuzé, On the report on the reversal of case law, a reaction between outrage and disbelief, JCP G 2005).

Beyond these academic quibbles, what is the situation today?

The current practice of modulation by French courts

In 2004, the Court of Cassation carried out its first modulation of the effect of case law over time (Cass. Civ. 2^E, July 8, 2004, no. 01-10.426).

In 2016, she detailed (Cass. Civ. 1^re, April 6, 2016, no. 15-10.552):

” while the new case law applies ipso jure to everything that has been done on the basis of and on the basis of old case law, the implementation of this principle may irreparably affect the situation of the parties who acted in good faith, by complying with the state of law applicable at the date of their action, so that the judge must carry out an assessment of the disadvantages justifying an exception to the principle of retroactivity of case law and find out, on a case-by-case basis, if it exists, between the advantages attached to it and its disadvantages, a manifest disproportion ”

Since then, the Court of Cassation seems to regularly modify its decisions over time to refuse the immediate application of new case law modifying the rules of procedure and whose application would deprive part of its right of access to the judge (Cass. Civ. 2^E, September 17, 2020, no. 18-23.626; Cass. Civ. 2^E, December 21, 2023, no. 21-22.239; Cass. Civ. 2^E, May 22, 2025, no. 22-22.868).

The modulation of the effects of case law over time therefore seems mainly confined to procedural issues and the guarantee of access to the judge.

However, it is possible that the Court of Cassation is in the process of evolving! This is evidenced by a decision where the Court of Cassation declared illegal a Polynesian practice of delegating parental authority developed on the fringes of legality, while deferring the effects of its decision to mitigate the consequences (Cass. Civ. 1^re, September 21, 2022, no. 21-50.042).

In conclusion, Master?

In conclusion, the retroactivity of case-law remains the rule: the Court modulates the effect of its case-law over time mainly for procedural reasons.

As it is, as your lawyer is not a fortune-teller, he will never be able to advise you beyond what the case law says.

Is he sure that this is the rule of law? By the time he advises you, you can hope so.

Does this guarantee that the judge will rule in this way? Unfortunately, no.

👉 Are you facing a legal problem? I am here to advise you and guide you through the maze of case law.

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