Intellectual property lawyer in Paris

Dhenne Avocats is a patent litigation firm. The point is worth making, because intellectual property covers trades that share neither the same courts, nor the same deadlines, nor the same instincts.

The firm argues patent disputes before the Paris Judicial Court, the Paris Court of Appeal and the Unified Patent Court. It handles the matters that attach directly to those cases: trade secrets and know-how, employee inventions, licences FRAND et brevets essentiels, contrats portant sur des brevets.

It does not file titles, does not manage trade mark portfolios and does not run copyright or design litigation for its own sake. That work belongs to other practitioners, with whom the firm works regularly.

Three features set the patent apart from the other intellectual property rights and explain why it calls for a dedicated practice.

It is proved technically. Infringement is established claim by claim, by comparison with a product or a process, which means reading a technical text as the skilled person would have read it at the priority date.

It can be attacked in defence. A defendant to an infringement action almost always raises the nullité du titre, which opens a second trial inside the first. No other intellectual property right shows that symmetry so systematically.

It belongs to specialised courts. The Paris Judicial Court has exclusive jurisdiction in France (art. L. 615-17 of the Intellectual Property Code). Since June 2023 the Unified Patent Court has opened a parallel European route. Opposition before the European Patent Office is a third ground, with deadlines of its own.

A patent dispute regularly crosses others. The firm handles them where they attach to the case, not as a practice of their own.

• Trade secrets, in claim and in defence, including protection of the secrets of the party searched during a saisie-contrefaçon.
• Unpatented know-how, often transferred by the same contracts as the patents.
• Copyright in software, where the same technical solution is claimed on two grounds.
• Unfair competition and free riding, where they are raised as related claims before the patent court.
• The additional remuneration owed to an employee inventor, and the classification of inventions.

The distinction is real and often misunderstood. The patent attorney drafts and files applications, runs prosecution and manages portfolios. The attorney at law appears before the courts, argues the case, runs the evidence-gathering measures and pursues the other side's liability.

In a contentious case both are involved, in distinct and complementary roles. The firm works routinely alongside the patent attorneys already in place, French and foreign, without displacing them.

Do you need an attorney at law or a patent attorney to sue for infringement?
Before the Paris Judicial Court and before the Unified Patent Court, representation belongs to the attorney at law. The patent attorney brings the technical analysis and the prosecution history, which makes cooperation between the two indispensable.

Does the firm file patents?
No. Filing, prosecution and portfolio management belong to patent attorneys. The firm works on the granted title, in attack, in defence and in the contracts that exploit it.

Can a patent be attacked without being sued first?
Yes. A revocation action requires no particular interest and is subject to no limitation period (art. L. 615-8-1 of the Intellectual Property Code). A company preparing a launch can therefore bring down a troublesome title before being sued.

A cease and desist letter received, a competitor copying, a saisie announced, a patent to bring down before a launch: the earlier the firm is instructed, the more procedural options remain open. Tell us about your situation.

Le cabinet a également structuré des offres et programmes à périmètre défini : second opinion, préparation au contentieux, protocole de réponse à une saisie-contrefaçon, audit du secret des affaires, due diligence en propriété intellectuelle, financement du contentieux.