Court of Justice of the European Union allows Reverse Engineering to Correct Errors
Licensees are in certain cases permitted to decompile software code without infringing the Software Directive. In a judgement of 6 October 2021 in the case C-13/20, the Court of Justice of European Union (CJEU) ruled that insofar decompiling is necessary to debug the software, regardless of whether it is prohibited by the license agreement, the licensee is free to do so without being subject to Article 6 of the Software Directive. However, the CJEU leaves the door open for parties to provide contractual provisions in order to agree on steps and procedures for bug fixes.
The CJEU came to this decision after a preliminary question of the Brussels’ Court of Appeal (C-13/20). The case revolved around Top System, a developer of computer programs. For several years Top System had been working for the Belgian public organisation Selor, building several digital applications and granting licenses thereof to Selor.
As Top System was experiencing persistent software malfunctions that could not be resolved, Selor decompiled part of the licensed software in order to disable the faulty function. Top System argued that this decompiling was not allowed and that Selor had thereby infringed its exclusive rights as regards to the software.
The Brussels’ Court of Appeal referred the matter to the CJEU for a preliminary ruling in order to clarify the extent to which decompiling of a computer program is permitted under European copyright law, in particular to Directive 91/250 of 14 May 1991 on the legal protection of computer programs (hereinafter the Software Directive) . The Brussels’ Court of Appeal formulated two questions in this regard:
- Is Article 5(1) of Software Directive to be interpreted as permitting the lawful purchaser of a computer program to decompile all or part of that program where such decompilation is necessary to enable that person to correct errors affecting the operation of the program, including where the correction consists in disabling a function that is affecting the proper operation of the application of which the program forms a part?
- In the event that that question is answered in the affirmative, must the conditions referred to in Article 6 of the Software Directive, or any other conditions, also be satisfied?
Decompiling in case of necessity to correct errors
The CJEU held that although Art. 4 of the Software Directive grants an exclusive right of reproduction to the creator of a computer program, Art. 5 of the same Directive stipulates that, in the absence of a provision in the license agreement, the licensee may perform acts necessary to use the computer program for its intended purpose, including correction of errors, without the consent of the copyright owner.
According to the CJEU, Art. 5 of the Software Directive should be interpreted as meaning that the legitimate purchaser of a program is entitled to decompile that program in order to correct errors affecting its operation and that Art. 6 of the Software Directive should not be understood as a being limited to interoperability purposes and therefore does not prevent such decompiling for bug fixes. The CJEU stated that “while Article 6 of [the Software Directive] concerns the acts necessary to ensure the interoperability of programs created independently, Article 5 (1) thereof seeks to allow the legitimate purchaser of a program to use it in a manner consistent with its intended purpose. These two provisions therefore have different purposes”.
Application of the Conditions of Art. 6 Software Directive
As Art. 5 and 6 of the Software Directive were considered to have different purposes, the CJEU concluded that the requirements set out in Art. 6 are not, as such, applicable to the exception provided for in Art. 5 (1) of the Software Directive.
However, this does not mean that there are no conditions for relying on Art. 5 of the Software Directive. According the CJEU, the acts must be “necessary” for the lawful acquirer to be able to use the program for its intended purpose, including the correction of "errors":
- “Errors”: according to the CJEU, the term “errors” must be interpreted in accordance with its usual meaning in everyday language, while also taking into account the context in which it occurs and the purposes of the rules of which it is part. In the field of computing, an error is generally seen as a defect affecting a computer program which is the cause of the malfunctioning of that program;
- “Necessary”: the correction of errors affecting the use of a program in accordance with its intended purpose will, in most cases, involve modification of the program code and the implementation of that correction will require access to the source code or, at the very least, to the quasi-source code of that program. In case the source code is lawfully or contractually accessible to the purchaser, the CJEU stated that the decompiling cannot be regarded as necessary.
On the other hand, the CJEU considered that the correction of errors may be subject to specific contractual provisions. In this regard, the CJEU had the following observations:
- Recital 18 of the Software Directive prevents IT developers to contractually prohibit both the loading and unrolling operations necessary for the use of a copy of a legally acquired program and the correction of errors affecting the operation thereof, meaning that parties cannot contractually exclude any possibility of making a correction of these errors;
- however, the parties can stipulate the procedures for exercising the right to decompile; for example, the parties can agree that the rightholder must ensure corrective maintenance of the program concerned; and
- in case the parties did not provide for any specific contractual provisions, the licensee shall be free to decompile the program insofar as this proves to be necessary in order to correct errors affecting the operation of the program. Of course, the licensee shall not be permitted to decompile for other purposes than correcting such errors.
From the CJEU judgment we learn that, in the absence of any contractual provisions, the licensee is permitted to decompile the licensed software insofar it is necessary for the licensee to be able to use the program for its intended purpose, including the correction of errors. The decompiling should however be limited to the purpose of correction of the errors and cannot be used otherwise.
Even though parties are prohibited from contractually excluding any possibility of making a correction of the errors, parties should consider addressing the conditions of the legitimate user’s decompiling activities in the license agreement, to avoid possible disputes.
 The Software Directive was repealed by Directive 2009/24/EC of 23 April 2009 on the legal protection of computer programs, which includes the same provisions.