Not entirely. Copyright law allows a lawful user, without the author's consent, to make a back-up copy of a program, to study and test how it functions, and to decompile the code to the extent necessary to achieve interoperability with another program. The EU directive which the Act implements declares contractual provisions contrary to those entitlements void from the outset. Licence terms should therefore prohibit what the law does not give the user: copying beyond the licence, disclosure of information obtained by decompilation, and its use to develop a similar program.
Licence terms taken over from foreign precedents almost always contain the same paragraph: the customer may not copy, disassemble, decompile or study the operation of the program. For software the customer installs on its own systems, a blanket prohibition of that kind does not stand up under either Slovak or Czech law. Part of it is valid and part is not, and in a dispute this becomes apparent precisely in the provision you are relying on.
What the law permits the user without your consent
Copyright law (Act No. 185/2015 Coll.) protects a program in both source and object code, but not the ideas and principles on which it rests (Section 87(1)). At the same time, it grants a person entitled to use a copy of the program several entitlements:
A lawful user does not interfere with the rights of the author of a computer program where, without the consent of the author of the computer program, he […] makes a back-up copy of the computer program for the purpose of securing the proper use of the computer program, […] examines, studies or tests the functioning of the computer program in order to determine the ideas or principles underlying any part of the computer program […]
— Section 89(2) of Act No. 185/2015 Coll. (unofficial English translation)
To this is added decompilation under Section 89(3): the user may reproduce or translate the code to the extent necessary to obtain the information required for interoperability with an independently created program, where that information was not previously readily available. No remuneration is due to the author for these acts (Section 89(4)).
Why a prohibition in a EULA does not stand up
As regards the back-up copy, the study of how the program functions and decompilation, Slovak law permits no contractual derogation; the reservation “unless otherwise agreed” applies only to ordinary use of the program, including the correction of errors (Section 89(2)(a)). Directive 2009/24/EC, on which the rules are based, is explicit on contractual prohibitions:
Any contractual provisions contrary to Article 6 or to the exceptions provided for in Article 5(2) and (3) shall be null and void.
Czech copyright law says the same thing directly in its text. It describes the user’s entitlements as a minimum scope which cannot be narrowed by agreement, save for modifications of the program necessary for its use (Section 66(6) of Act No. 121/2000 Coll.). For a product sold on both markets, the conclusion is therefore the same.
What you may and should prohibit instead
The statutory exceptions are narrow and precisely delimited, and it is at their boundaries that a EULA should aim. Information obtained by decompilation may not be used for any purpose other than interoperability between programs, may not be given to others save where strictly necessary, and may not be used to develop a program similar in its expression (Section 89(3)(a) to (c)). The user may not use the program contrary to its ordinary use or unreasonably interfere with your interests (Section 89(1)). You may reserve the correction of errors to yourself, because there the law does permit a contractual derogation.
Licence terms should therefore state the number of devices or users, prohibit rental and sub-licensing, prohibit circumvention of the licence key, prohibit the use of information obtained by decompilation to develop a similar program, and require the customer to approach you first if it needs information about interfaces. If you publish that information in your documentation, the ground for decompilation for interoperability will generally fall away, because the information will be readily available.
How to proceed
Review your EULA and replace the blanket prohibition with a provision which respects the statutory exceptions and defines precisely what is prohibited beyond them. A provision drafted in this way can actually be enforced against the customer. We prepare licence terms tailored to the product under licence terms (EULA), and individual licences for corporate customers under the software and licence agreement. If a customer who bought a licence from you wishes to resell it, see the question on the resale of a used software licence.
This answer provides general information on the law as at 12 September 2026. It does not constitute legal services or replace an assessment of an individual case. The details of your situation may differ. Book a consultation to discuss them.
