Illegal Planning Permission: The Plea of Illegality Admissible on Appeal Even After Rejection of Direct Challenge

Imagine : you are an owner in Digoin, a small peaceful town in Saône-et-Loire. One morning, you discover that your neighbour has started constructing a concrete terrace that encroaches on your view and threatens rainwater drainage. You consult the planning permission displayed at the town hall and realise it was granted in flagrant breach of the local urban development plan (PLU). You rush to challenge it, but… too late : the two-month time limit for challenge has expired. What can you do ?

This question is asked by hundreds of owners every year. The good news is that a judgment of the French Court of Cassation of 8 February 1995 (the Le Grand Carénage case) offers a lifeline : the plea of illegality. Even if your direct challenge against the permission has been rejected as out of time, you can still, in the context of civil proceedings (for example, a claim for demolition), raise the illegality of that permission for the first time on appeal. Provided you do so before any defence on the merits.

This judgment, handed down nearly thirty years ago, remains highly relevant today. It allows litigants not to be trapped by an unlawful administrative act, even when they have missed the time limit for challenge. A full analysis of this decision and its practical implications, with examples drawn from practice in the jurisdictions of Chalon-sur-Saône, Digoin and Montceau-les-Mines.

The facts : a story like those that happen every day

In 1982, the development company (SCI) Le Grand Carénage obtained a planning permission for a hotel complex in the commune of Digoin. Everything seemed in order… until Mrs X and several co-owners (owners of plots in a neighbouring housing estate) noticed that the project far exceeded the heights permitted by the local land use plan (POS) and encroached on rights of way. Furious, they sued the SCI in court to obtain an immediate halt to the works and, later, demolition of the constructions.

But here’s the thing : in the meantime, the co-owners had also applied to the administrative court to challenge the planning permission. The Conseil d'État, hearing the case at final instance, declared their claim inadmissible as out of time : they had exceeded the two-month period following the display of the permission. This administrative decision seemed to seal their fate.

Yet, before the civil court (the High Court and then the Court of Appeal), the co-owners continued to argue that the permission was unlawful, and therefore that the construction should be demolished. The SCI, for its part, argued that the illegality of the permission could no longer be raised, since the Conseil d'État had definitively closed the debate. The Dijon Court of Appeal (jurisdiction of Chalon-sur-Saône) ruled in their favour on the merits : it ordered demolition. The SCI appealed to the Court of Cassation.

The reasoning of the court — dissected

In its judgment of 8 February 1995, the Court of Cassation had to decide a crucial procedural question : can a plea of illegality (a means by which the validity of an administrative act is challenged in the context of civil proceedings) be raised for the first time on appeal, after the direct challenge for annulment has been declared inadmissible ?

The reasoning of the judges of the High Court revolves around two fundamental principles. First, the principle of separation of administrative and judicial authorities (law of 16-24 August 1790) : the civil court cannot annul a planning permission, but it can note its illegality incidentally, in order to draw the consequences for the rights of the parties. Second, the principle of the relative effect of res judicata : the inadmissibility of the direct challenge does not mean that the permission is lawful ; it means only that the applicant no longer has the possibility of having it annulled by the main route.

In this case, the co-owners had not yet presented a defence on the merits before the Court of Appeal when they raised the plea. It was therefore raised in time. The Court of Cassation validates their approach : “the plea of illegality of a planning permission is admissible when raised for the first time before the Court of Appeal, before any defence on the merits, after the Conseil d'État has merely declared the application for annulment of the planning permission inadmissible as out of time.”

This judgment constitutes a confirmation of previous case law (Civ. 3rd, 17 March 1993, Bull. III, No. 40) and not a reversal. It reaffirms that the plea of illegality is a subsidiary avenue that remains open, even on appeal, provided that procedural formalities are respected. The judges rejected the SCI’s argument that a preliminary question (request for a stay of proceedings addressed to the administrative court) had to be raised. Here, the illegality was sufficiently obvious for the civil court to note it directly.

What this changes for you — concretely

Are you an owner in Montceau-les-Mines, and has your neighbour built an extension that blocks your view of the canal ? Did you not challenge the permission within two months ? Rest assured : you can still act. But on one condition : that you have ongoing civil proceedings (for example, an action for demolition based on abnormal neighbourhood disturbance). In those proceedings, you can raise the illegality of the permission for the first time on appeal, if you did not do so at first instance.

Concrete example : let us imagine that the illegal construction causes a loss in value of your house estimated at €30,000. If you succeed on the plea of illegality, the civil court can order demolition or damages. Without this judgment, you would have no remedy.

However, note : the plea of illegality must be raised “before any defence on the merits”. Concretely, in your appeal submissions, as soon as you challenge the merits of the dispute (for example, by seeking demolition), you can no longer raise the plea. So you must act quickly and with a lawyer who masters the procedural subtleties.

For tenants : if you rent a property built on the basis of an unlawful permission, you can also invoke this plea to claim a rent reduction or termination of the lease for disturbance of enjoyment. Real estate professionals (developers, builders) must, for their part, redouble their caution : an apparently final permission can be challenged years later, by way of a plea on appeal.

Four tips to avoid this type of dispute

• Anticipate challenges : as soon as the permission is displayed, take a photo of the notice and note the date. If you suspect an illegality, consult a lawyer within the two-month period. A direct challenge remains the safest route.
• Keep all evidence : letters, photos, bailiff’s reports. If the time limit for challenge has passed, these elements will support your plea of illegality before the civil court.
• Act without delay : as soon as the disturbance appears (loss of view, encroachment), start proceedings on the merits. The plea of illegality can only be raised if civil proceedings are pending.
• Be vigilant on appeal : if you lost at first instance, raise the plea only after having appealed and before concluding on the merits. A specialised lawyer will guide you on timing.

Further analysis : related case law and developments

This decision is part of a consistent line of the Court of Cassation. Already in 1993 (Civ. 3rd, 17 March 1993, Bull. III, No. 40), the judges had admitted the plea of illegality on appeal in a similar case. More recently, the Court of Cassation clarified that the plea can be raised even if the permission was subsequently annulled by the administrative court (Civ. 3rd, 10 March 2021, No. 19-24.236).

The trend is therefore towards the protection of the litigant : the courts want to prevent an unlawful administrative act from producing harmful effects indefinitely. However, this avenue is not open in all circumstances : there must be ongoing civil proceedings and a link between the permission and the damage. The future may see legislative adjustments, but for now, this 1995 judgment remains an essential reference.

Summary and next steps

FAQ :

• What is a plea of illegality ? It is the act of challenging the validity of an administrative act (such as a planning permission) in the context of civil proceedings, without seeking its direct annulment.
• Can I still challenge a permission after two months ? Yes, by way of a plea, but only if civil proceedings are ongoing (e.g., an action for demolition).
• Can I raise the plea for the first time on appeal ? Yes, provided you do so before any defence on the merits (before presenting your arguments on the substance of the dispute).
• What should I do if I am in this situation ? Consult a lawyer specialising in property law quickly. He or she will check whether you are still within the time limits to act and will assist you in drafting your submissions.
• How much does an action for demolition cost ? Solicitor's fees vary, but a first 30-minute consultation at €45 can clarify your chances of success.

Are you in a similar situation ? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →