Planning Permission: When the Law Changes, the Conviction Falls (Cass. crim., 17 Feb. 1987)

You have just bought a plot of land in Bayonne, with a view of the Pyrenees. You install a greenhouse for your orchids without a second thought. A few months later, the postman hands you a summons to the criminal court: "failure to obtain planning permission". You thought everything was in order. But what if, between the time of construction and your trial, the law has changed and now authorises this type of structure without permission? This decision of the Court of Cassation of 17 February 1987 directly concerns you.

The question every owner asks: can I be convicted for a construction that, at the time of judgment, has become legal? The magistrates' answer is clear: no. The principle of the application of the more lenient criminal law (a constitutional principle) protects the defendant. The commented judgment is a perfect illustration of this.

But beware: it is not enough for the law to change after the facts to be automatically acquitted. The new regulations must also abolish the offence or reduce the penalty. And above all, the replacement formalities (such as the prior declaration) must have been completed. This decision is a textbook case, but also a warning: better to anticipate.

The facts: a story that happens every day

Mr X, an owner in Bayonne, decided in 1984 to build greenhouses on his land. He did not apply for planning permission. Why? Because at the time, local regulations did not subject greenhouses to this formality. So he built quietly.

But the town hall saw the works, issued a ticket, and the public prosecutor prosecuted him for building without permission. On 7 January 1986, the Angers Court of Appeal found him guilty and fined him 800 francs (about 122 euros), with an order to restore the site to its original state.

In the meantime, two texts were adopted: the Law of 6 January 1986 and the Decree of 14 March 1986. These texts modified the planning rules: for greenhouses like Mr X's, planning permission was no longer required. A simple prior declaration sufficed. Mr X did not make a declaration, but the law was more lenient. He appealed to the Court of Cassation.

The twist: the Court of Cassation ruled in his favour. It quashed the Angers judgment, holding that the judges should have applied the new, more favourable law. The case was remitted to another Court of Appeal.

The reasoning of the court — dissected

The Court of Cassation relied on a fundamental principle of criminal law: the immediate application of the more lenient criminal law. This principle, enshrined in Article 112-1 of the (new) Criminal Code, means that a person cannot be punished more severely than provided for by the law in force at the time of judgment.

In this case, the offence of building without permission existed at the time of the facts. But the Law of 6 January 1986 and the Decree of 14 March 1986 abolished the requirement for permission for greenhouses, replacing it with a simple declaration. However, the declaration is not itself a criminal offence: its absence may give rise to an administrative fine, but not to a criminal conviction with an order to make the building compliant.

In other words, the new regulations decriminalised (transformed into a mere administrative formality) the disputed construction. The Angers judges should have taken this into account. By failing to do so, they violated the principle of retroactivity in mitius (application of the more lenient law).

What few people know is that this principle applies even if the defendant has not complied with the new formalities. The Court of Cassation is clear: the offence no longer exists in criminal law. However, the administration may require a subsequent declaration and impose an administrative fine.

What this changes for you — practically

This decision has important practical implications for owners, purchasers and property professionals.

• For the landlord owner: if you built a greenhouse, garden shed or extension without permission a few years ago, and the regulations have changed in the meantime, you cannot be criminally convicted. Example in Anglet: in 2020, you build a 20 m² pergola without a declaration. In 2023, the law lowers the declaration threshold to 15 m². If you are prosecuted after 2023, you will be acquitted, because at that date your construction is no longer subject to permission.
• For the purchaser: before buying a property, check whether recent constructions have been carried out with or without authorisation. If the seller was convicted and then acquitted due to a change in the law, the criminal offence is erased, but the absence of a declaration may cause problems for a future planning application or sale. Worked example: in Bayonne, a 30 m² garage built without permission in 2018 is now compliant if the local plan (PLU) has been amended. But without a declaration, you will have difficulty obtaining a mortgage.
• For the tenant: you are not directly concerned, but if your home includes an unauthorised construction, be aware that the owner may be forced to demolish it despite a change in law, if the administrative offence persists.
• For the co-owner: if the co-owners' association carries out works without permission, each co-owner may be prosecuted. But a change in the law benefits everyone.

If you are in this situation, you must check the date of the facts and the law in force at the time of judgment. undefined, I have come across cases where owners had been convicted for garden sheds that had become legal. Thanks to this case law, we obtained the quashing of the convictions.

Four tips to avoid this type of dispute

• Check the local plan (PLU) before any construction: the Local Urban Plan (PLU) of Bayonne or Anglet sets the rules. A simple pergola may require permission if it exceeds 5 metres in height. Do not rely on what the seller or neighbour says.
• Make a prior declaration even if in doubt: it is free and quick (1 month processing time). This will save you from criminal prosecution. Example: in Anglet, an individual installed a 12 m² garden shed without a declaration. He was fined €1,500. With a declaration, he would have been in compliance.
• Keep proof of your steps: receipt of declaration, permit, photos of the works. In the event of an inspection, you can prove your good faith.
• Consult a lawyer before starting works: preventive advice costs less than legal proceedings. Maître Zakine can help you analyse your project.

Besoin d'un conseil personnalisé ? Contactez Maître Zakine — première consultation 30 min à 45€.

In-depth: related case law and developments

This decision is part of a consistent line of case law from the Court of Cassation. For example, in a judgment of 8 March 1989 (No. 87-84.215), the Criminal Chamber held that the repeal of an incriminating text after the facts led to an acquittal, even if administrative formalities remained.

However, beware of the distinction between decriminalisation and a mere change of thresholds. If the new law maintains the offence but reduces the penalty, the principle also applies. But if it creates a new formality (such as the declaration), the failure to declare may be sanctioned administratively.

The recent trend is towards decriminalisation of many planning offences, transformed into high-way contraventions or administrative sanctions. This means that owners must be doubly vigilant about declaratory formalities.

What you must absolutely remember

1. If the law changes after your construction, you cannot be criminally convicted for an offence that has become legal.
2. But you must regularise your situation by a prior declaration, otherwise the administration may impose a fine (up to €1,200) and order demolition.
3. Keep all evidence of the date of construction: photos, invoices, attestations. Without them, you will not be able to prove that the law in force at the time of the facts was different.
4. If prosecuted, do not plead alone: a lawyer specialised in property law can invoke the principle of the more lenient criminal law and have the conviction quashed.
5. Before buying a property, have a notary or lawyer check the compliance of existing constructions. Non-compliance can block the sale or lead to costly works.

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 →