May a former employee take source code to a competitor? Software and trade secrets

The short answer is no. When an employee leaves a company, he may not take or retain source code, software structures or technical documentation, even in a “private folder” or for “study purposes.” Using such data for competitive activity generally constitutes both copyright infringement and violation of trade secrets, which can lead to immediate cease-and-desist orders and heavy fines.

The facts: competition after dismissal

In a case before the President of the Dutch-speaking Enterprise Court in Brussels, a software company and two former employees faced off.

The facts were as follows:

• Two employees, active developers, left the company in December 2024.
• Shortly after they left, they launched a competing initiative with similar services.
• The software company suspected that the former employees had not started “from scratch” but had copied parts of its own software code.
• Through a unilateral petition, the company obtained permission to establish a seizure order regarding counterfeiting . In the process of this seizure, source code from the software company was found on the computer of one of the ex-employees in a protected folder (see our earlier blog).

The ex-employees defended themselves by arguing that they had developed the code independently, that similarities were due to industry standards, and that the copy found was only in a “test folder” and not used operationally.

The court's decision

The president of the Enterprise Court ruled in favor of the software company in a judgment dated Jan. 15, 2026. The president found that there were two separate infringements:

1. Copyright infringement: The court ruled that the former employees infringed on the copyright of the software company by copying and editing the software. The defense that it was merely a “private copy” or that the code served to “observe and test” (as permitted for lawful users under Art. XI.299 CEL), was rejected. This exception, according to the president, does not apply to former employees who compete after their resignation.
2. Breach of trade secrets: The source code, documentation and structure of the software were recognized as trade secrets. Retaining this code after leaving employment, in violation of contractual confidentiality clauses, was labeled as unlawful use.

The president ordered the immediate cessation of the use of the software and the destruction of all files, under penalty of a fine of 10,000 euros per day, with a maximum of 500,000 euros.

Legal analysis and interpretation

This ruling shows a strict attitude toward data theft by personnel. Some legal nuances are crucial to the practice:

Copyright originality in software

A common defense in software cases is that code is “determined by technology” and therefore not protected. The president dismisses this in this case. According to the president, the originality threshold for software is low: it is sufficient that the code is the result of “free and creative choices.” Elements such as the structure, naming conventions of variables and comment lines are expressive. When these recur identically in a competitor, it is a strong indication of copying behavior, unless one can prove an outside source (such as open source).

The pitfall of Article XI.299 CEL

The defendant invoked Article XI.299 CEL, which allows a lawful user to observe and test software to understand its operation. The president did not follow this: this exception does not serve to give former employees a “right to retain” source code after their dismissal. Once the employment contract ends, the lawful use ends.

Evidential value of the seizure regarding counterfeiting

The judgment shows the value of the seizure regarding counterfeiting (art. 1369bis Ger.W.). Although this is a one-sided proceeding, the president ruled that technical determinations (such as file names and structures) serve as valid evidence. Even if code is not “live” but is in a “forgotten” folder, its possession by a competitor violates fair trade practices.

What this specifically means

This judgement has direct implications for employers and IT professionals:

• For employers (software companies):
  • Contracts are essential: Ensure watertight intellectual property and confidentiality clauses in employment contracts. The court relied heavily on the contractual duty of confidentiality to establish violation of trade secrets.
  • Action on suspicion: If you suspect a former employee has taken code, speed is of the essence. A seizure regarding counterfeiting is often the only way to secure evidence before it is erased or altered.
  • Solidarity: You can often hold all those involved (both the ex-employee and his new company or business partners) accountable, even if the code is found in only one person.
• For employees and developers:
  • Clean slate: If you start your own business, really start from scratch. “Refactoring” or rewriting existing code from your former employer is still an infringement (adaptation).
  • No souvenirs: Keeping code in a private folder “to look at again” or for your portfolio is life-threatening. The court does not accept the excuse of “non-operational use.”.
  • Knowledge vs. Data: You may bring your general knowledge and experience (your “skillset”), but not the actual data, code or documentation from your previous employer.

FAQ: Frequently asked questions

Can I take home code I wrote myself while working?
No, unless otherwise agreed. Software written in execution of the employment contract belongs to the employer (Art. XI.296 CEL). Taking it with you after dismissal is theft of intellectual property and/or trade secrets.

Is changing variable names enough to avoid copyright infringement?
No. Copyright law also protects the structure and organization of code. Systematically modifying or “translating” code is considered an adaptation, which requires permission.

What is a seizure regarding counterfeiting?
This is a procedure in which a bailiff and an IT expert, after permission from the court, drop in unexpectedly to determine and describe evidence of infringement (such as copies of software). This can be done at businesses as well as at individuals' homes.

Conclusion

The dividing line between permissible competition and tort is thin, but is crossed in Belgium as soon as digital files of the ex-employer are involved. For technology companies, the protection of their source code (the “crown jewels”) is vital.