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Sometimes, but there is no blanket yes or no. Whether decompiling a game is lawful depends on the country, why and how you obtained and analyzed the copy, whether you bypassed technical protections, what you copied, and what you do with the results. In the United States, copyright fair use and the DMCA’s anti-circumvention rules are separate questions; the European Union has a limited exception for decompilation needed for software interoperability.
Why the answer depends on more than owning a copy
Decompilation can involve reproducing or translating copyrighted code to understand how a program works. A lawful copy may matter, but buying or otherwise possessing a game does not, by itself, settle whether a particular decompilation is allowed. The purpose and scope of the analysis, access controls, license terms, and later use of what you learn can all affect the legal assessment.
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It helps to separate two issues. Copyright law asks whether copying is permitted, for example under fair use in the United States. Anti-circumvention law asks whether bypassing a technological measure that controls access is permitted. A favorable answer to one does not automatically answer the other.
What the U.S. Sega case does—and does not—establish
In Sega Enterprises, Ltd. v. Accolade, Inc., the Ninth Circuit considered an independent game developer’s effort to learn the compatibility requirements for Genesis cartridges. Accolade bought a console and commercially available cartridges, disassembled their object code, and produced a development manual describing functional interface requirements rather than Sega’s code.
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The court concluded that, on that record, the disassembly was fair use. Its analysis considered the purpose and character of the use, the nature of the software, the amount copied, and the effect on the market. The first, second, and fourth factors favored Accolade; the third weighed in Sega’s favor, but only slightly. The court explained: “In light of the public policies underlying the Act, we conclude that, when the person seeking the understanding has a legitimate reason for doing so and when no other means of access to the unprotected elements exists, such disassembly is as a matter of law a fair use of the copyrighted work.”
That is a fact-specific Ninth Circuit decision, not a general authorization to decompile any game. Its reasoning concerned access to unprotected functional elements for a compatibility effort. It does not establish that copying expressive code into a new game, distributing proprietary material, or decompiling for another purpose is fair use.
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Why the DMCA creates a separate question
Even if a copyright argument supports copying for analysis, bypassing a technical protection can raise a distinct issue under 17 U.S.C. § 1201. The U.S. Copyright Office describes the DMCA as generally prohibiting circumvention of technological measures that protect copyrighted works, including software and video games. Its statutory text includes a limited interoperability provision in § 1201(f).
Conditions for the U.S. interoperability provision
Section 1201(f) is narrowly framed. It concerns a person who has a lawful right to use a copy of a computer program and circumvents a protection solely to identify and analyze elements necessary for interoperability with an independently created program, when those elements are not readily available. The statute also limits how information or tools obtained through that process may be shared or used, and does not excuse infringement or violations of other applicable law.
The Copyright Office also runs a triennial process for limited, temporary exemptions from certain anti-circumvention prohibitions. The ninth proceeding’s final rule is dated October 28, 2024; the existence of that process does not establish that a particular game or project is covered. See the Office’s 2024 Section 1201 proceeding.
The European Union’s interoperability exception
Article 6 of Directive 2009/24/EC provides a conditional route to decompilation without the rightsholder’s authorization when reproducing or translating code is indispensable to obtain information needed for interoperability of an independently created program.
The exception requires that the person be entitled to use the program copy, that the necessary information is not already readily available, and that the decompilation be limited to the parts necessary to achieve interoperability. Information obtained under the exception cannot be used for other goals, disclosed except as needed for interoperability, or used to develop a program substantially similar in its expression. This summary does not address how an individual EU country has implemented the directive or how its courts apply it.
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How to assess a specific game project
Before treating decompilation as permissible, work through the facts that can change the analysis:
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- Where will the work happen? Identify the jurisdictions where you access and analyze the game, develop any resulting software, and distribute it. The U.S. and EU rules described above are not interchangeable, and other countries may apply different law.
- What is the purpose? Interoperability, research, preservation, security analysis, modification, and development of a competing game are different purposes. The U.S. interoperability provision and EU directive exception specifically focus on interoperability with an independently created program.
- How did you obtain the copy and access? Establish whether you had a lawful right to use the copy and check the applicable license. Also determine whether reaching the relevant code required bypassing a technological measure.
- Was decompilation necessary and limited? Consider whether the information was already readily available and whether you can confine analysis to the portions needed for the stated purpose.
- What will you retain or share? Distinguish functional interface information from copied game code. Consider whether you will publish findings, share tools or circumvention methods, or incorporate code into another work.
- What other obligations apply? Contract terms, trademark, trade-secret, privacy, security, and other laws may raise separate issues beyond copyright and anti-circumvention rules.
These questions can identify legal issues, but they do not yield a definitive answer without the project’s facts and the law of the relevant jurisdiction.
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