Decompilation of software for error correction: CJEU judgment in Top System

Spain European Union

Judgment confirming that the purchaser of software may decompile it for bug fixes

Decompilation of software for error correction: CJEU judgment in Top System
November 4, 2021

In its judgment in Case C-13/20, the Court of Justice of the European Union (“CJEU”) concluded that the lawful acquirer of a computer program may decompile it, fully or partially, to correct errors that affect the program’s functioning. According to the judgment, this decompilation is allowed under article 5, on error correction, of Directive 91/250 (which is applicable to the case due to the timing of the facts, although the applicable provisions have the same wording as those of Directive 2009/24/EC, the “Directive”), and not necessarily under article 6 of the Directive, governing decompilation for interoperability purposes.

We discussed Advocate General Szpunar’s Opinion on this blog in an entry summarizing the facts and circumstances giving rise to the main dispute and sharing the questions that the Belgian court referred for a preliminary ruling. For ease of reading, see these questions summarized below.

Facts of the case and questions referred for a preliminary ruling

The dispute giving rise to the questions referred for a preliminary ruling involves Top System, a Belgian company that develops computer programs, and the Belgian State. The case is about a decompilation by the Selection Office of the Federal Authorities (“Selor”) of a computer program called Top System Framework or “TSF” developed by Top System. This program is part of an application for which Selor holds a user license. Top System argues that the decompilation of TSF by Selor constitutes an infringement of its exclusive rights in this software, and thus claimed damages for the decompilation and copying of the source codes.

The Brussels Court of Appeal referred two questions for a preliminary ruling to the CJEU to clarify: (i) the interpretation of article 5(1) of the Directive, and particularly whether it allows a lawful acquirer of software to decompile it, fully or partially, to correct errors affecting the program’s functioning; and (ii) if so, whether the decompilation must fulfill the requirements laid down in article 6 of the Directive.

The possibility of decompiling a program for error correction

Article 5 of the Directive, on the exceptions to rightholders’ exclusive rights on a computer program, provides the following:

"1. In the absence of specific contractual provisions, the acts referred to in Article 4 (a) and (b) shall not require authorization by the rightholder where they are necessary for the use of the computer program by the lawful acquirer in accordance with its intended purpose, including for error correction.”

See below the acts referred to in article 5 and falling under the scope of the rightholder’s exclusive rights:

> To do or to authorize the permanent or temporary, full or partial reproduction of a computer program by any means and in any form, without prejudice to the exceptions provided in articles 5 and 6 of the Directive; and

> To do or to authorize the translation, adaptation, arrangement and any other alteration of a computer program and the reproduction of the resulting program.

So, decompilation is not one of the acts listed in article 4 to which article 5 refers. Therefore, the case requires verifying (i) whether the acts necessary for decompilation implement any of the acts listed in article 4(a) and (b) of the Directive, which are exclusive to the holder of the copyright in a computer program; and (ii) thus, whether they are covered by the exception provided in article 5.

In line with AG Szpunar’s Opinion, the CJEU notes that a computer program is initially written in the form of a ‘source code,’ i.e., in a comprehensible programming language, before being transcribed into a functional form that the computer can understand, i.e., into the form of an ‘object code,’ through a process called ‘compilation.’ Conversely, the purpose of ‘decompilation’ is to reconstruct the source code of a program from its object code.

Once again, the CJEU refers to AG Szpunar’s Opinion and reiterates that decompilation does not give access to the original source code, but to a ‘third’ version of the relevant program, which could be compiled into an object code, allowing that program to function. Therefore, decompilation entails altering the program’s code, which involves a reproduction of that code, and a translation of its form.

From a legal perspective, decompilation entails the reproduction and alteration of the code, which are both acts covered by the rightholder’s exclusive rights under article 4(a) and (b) of the Directive to which article 5 refers (exceptions to the restricted acts).

Based on this analysis, the CJEU concludes that the lawful acquirer of a computer program may decompile software to correct errors affecting the program’s functioning without the rightholder’s authorization. According to the CJEU, this conclusion applies despite that article 6 of the Directive (examined in detail below) regulates decompilation for the purpose of obtaining the information necessary to achieve the interoperability of an independently created computer program with other programs. The CJEU highlights that these two provisions have different purposes, and no Directive provisions suggest that EU lawmakers intended to allow for the reproduction and translation of the code only for ensuring interoperability.

Requirements for decompilation

The CJEU recalls the purpose and scope of articles 5 and 6 of the Directive. Under article 5(1), lawful acquirers can use software in accordance with its intended purpose. Article 6 has a different approach: allowing for decompilation for interoperability reasons (i) is unrelated to the normal use of software; and (ii) has a different purpose, i.e., the interoperability with other independently created programs. Therefore, the requirements of article 6 do not apply if decompilation is performed within the scope of article 5 (i.e., to use the program in accordance with its intended purpose).

However, the CJEU notes that decompilation still has to fulfill certain requirements. In particular, decompilation: (i) must be intended for error correction; (ii) should be necessary to allow the lawful acquirer to use the relevant software in accordance with its intended purpose; (iii) must be performed subject to “the specific contractual provisions,” which should not preclude any possibility of correcting errors, although they may regulate how error correction is exercised; and (iv) the lawful acquirer that decompiled the program must not use the results of this decompilation for purposes other than error correction.

The CJEU points out that errors are defects preventing the use of software in accordance with its intended purpose. However, unlike AG Szpunar in his Opinion, the CJEU does not delve into the interpretation of the concept of error. As noted by AG Szpunar, this can give rise to a dispute between the author and the lawful user of that program and, in AG Szpunar’s opinion, the concept of error does not include the technical obsolescence of software due to technological developments. Therefore, any acts addressing this obsolescence fall within the rightholder’s exclusive rights.

Based on the above, the CJEU concludes that lawful acquirers of computer programs may decompile these programs for error correction without having to fulfill the requirements laid down in article 6 of the Directive. But the decompilation must be performed to the extent necessary for this error correction and complying with any contractual conditions provided by the holder of copyright in the computer program.


A relevant consequence of the requirements laid down in article 6 not being applicable to article 5(1) is that lawful acquirers are not required “to ask the rightholder to correct the errors, to request access to the program’s source code, or to bring legal proceedings seeking an order that the rightholder perform a particular act.” However, decompilation is a time-consuming and expensive process with uncertain effects. Therefore, in practice, the rightholder’s cooperation could be relevant in any case, which underlines the importance of considering the limit of article 5(1) in licensing contracts.

Regarding the possibility of contractually limiting the application of article 5(1), we must examine the extent to which this could constitute abuse of dominance by the rightholder in certain cases (e.g., if there is no objective justification for this restriction; if the restriction is discriminatory; or in case of monopolistic positions); or if rightholders become so vulnerable at some point-particularly in a digital environment where controlling these situations is particularly difficult-that these restrictions become justified.

In any case, obviously there is a close connection between intellectual property law and competition law when the legal monopoly granted by the first to promote innovation ends up precisely hindering innovation. Once again, what scholars call the “incentive-access dilemma,” i.e., the balance to be secured between private and public interests, is on the table.

November 4, 2021