Emulators have always been a gray area. Googling the laws on emulation reveals all sorts of different answers, often with people saying that it's ok because "it's old stuff anyways."

Are there laws in place (in the US) that prohibit emulation of older operating systems/game systems?


3 Answers 3


Note of course that I'm not a lawyer, this is not legal advice etc. The laws that apply here are "intellectual property" laws: copyright, patent law and perhaps trademark law.

Emulators themselves aren't a gray area; some companies have tried to make them perceived as such. If you can write an emulator without violating anyone's copyright, then you're OK; any patents on old hardware will have expired.

The gray area concerns obtaining software to actually use the emulators, in some cases. Typically you want to use an emulator to run software (including possible firmware) that was relevant at the time; obtaining this software in a legal fashion can be difficult. In some cases, the rights-holders have explicitly allowed their firmware and/or software to be used in emulators, or provide licenses to do so (e.g. Amstrad for their old ROMs, HP with their hobbyist program...). In other cases, the rights-holders vehemently oppose any unsanctioned use of their software in emulation (unsanctioned typically meaning "not sold by them"), even if you own the originals. And in the remaining cases, the rights-holders are no longer around, or no one can figure out who owns the rights... If you own the original hardware (where relevant, e.g. for ROM chips) and software, you're probably OK.

Basically, as clarified by David Schwartz, emulators themselves are legal, and so is using them. Obtaining software for them may be illegal but that's another matter. Is it legal to download ROM images from shared or internet archives? has more on that topic.

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    Again, not a lawyer, but patents usually cover specific ways of doing things. If you can do in software what someone else patented in hardware, you're probably safe.
    – Mark
    Commented Dec 20, 2016 at 21:24
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    Copyright won't help them. At least in the United States, the ordinary use of a work by someone who acquired it legally cannot be restricted by copyright. Executing a software work in a suitable environment for its execution is ordinary use -- it's not copying, it's not distributing, it's not making the work available to the public -- it's not any of the things US copyright law reserves to copyright holders. Commented Dec 20, 2016 at 22:08
  • @DavidSchwartz "Copyright won't help them" — it does mean you can't just download any old piece of software from the Internet and assume you can legally run it in an emulator. I agree with the rest of your comment! Commented Dec 20, 2016 at 22:15
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    @StephenKitt You also can't shoot someone and then use an emulator. Yes, you can't do something illegal and then use an emulator. But that has nothing to do with the emulation, that's because the thing you did before you even touched the emulator was itself illegal. Commented Dec 20, 2016 at 22:17
  • @DavidSchwartz Ah yes, I see what you mean. The illegal act isn't the use of an emulator, it's the download itself. Commented Dec 20, 2016 at 22:24

There doesn't seem to be any law that prohibits it specifically. The most relevant law appears to be:

17 U.S. Code § 102 - Subject matter of copyright: In general

(b) In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.

Emphasis mine. My interpretation: emulators are computer programs that replicate the method of operation of the system being emulated, therefore they do not infringe any copyright.

Indeed, I wasn't able to find a case where "compatible products" such as emulators are outright asserted to be illegal. In the two relevant cases I found, the company took issue with something other than the emulator itself.

Two companies developed and sold PlayStation emulators and were subsequently sued by Sony. In those cases, Sony didn't try to dispute the legality of emulation. They sought an injunction that would stop the developers from making money off of the software. This stifled future development of their emulators. As noted in Aaron's Computing History:

Of course, as was widely reported, we were sued by Sony Computer Entertainment of America, and the legal tussle ensued. Although we won a number of battles, we lost the most important one: SCEA was granted a preliminary injunction against the product, which meant that we had to stop selling it shortly after we released it — and before I could finish up the Windows port. Unfortunately, this put the brakes on all our momentum, and generally hurt our ability to sell the product even after the injunction was overturned on appeal. Plus, since we didn't know whether or not the injunction was going to be overturned, it wasn't in our best interests to devote company resources toward improving the product. So it languished for several months, and a lot of features we wanted to put into it never made it. Eventually, we did ship the Windows version and a few updates, but by then the excitement and novelty of the product had long since worn off.

In the end, we managed to settle things out of court.

A summary of the two cases in question:

  • Sony Computer Entertainment v. Connectix Corp.

    Apparently, the issue was in how the PlayStation emulator came to be developed, rather than the fact it was developed at all.

    The Virtual Game Station does not contain any of Sony's copyrighted material. In the process of producing the Virtual Game Station, however, Connectix repeatedly copied Sony's copyrighted BIOS during a process of "reverse engineering" that Connectix conducted in order to find out how the Sony PlayStation worked. Sony claimed infringement and sought a preliminary injunction.

    Sony won at first but lost when Connectix appealed; the copying of the copyrighted PlayStation BIOS was found to be fair use, "necessary to permit Connectix to make its non-infringing Virtual Game Station function with PlayStation games".

    The object code of a program may be copyrighted as expression, 17 U.S.C. § 102(a), but it also contains ideas and performs functions that are not entitled to copyright protection. See 17 U.S.C. § 102(b). Object code cannot, however, be read by humans. The unprotected ideas and functions of the code therefore are frequently undiscoverable in the absence of investigation and translation that may require copying the copyrighted material. We conclude that, under the facts of this case and our precedent, Connectix's intermediate copying and use of Sony's copyrighted BIOS was a fair use for the purpose of gaining access to the unprotected elements of Sony's software.

    Sony also claimed Connectix's Virtual Game Station tarnished the PlayStation trademark because the emulator was unable to play games as well as the hardware. However:

    This evidence is insufficient to support a conclusion that the shoddiness of the Virtual Game Station alone tarnishes the Sony mark. Sony's tarnishment claim cannot support the injunction.

  • Sony Computer Entertainment America v. Bleem

    In this lawsuit, Sony simply claimed Bleem could not use screenshots of Sony's copyrighted games to advertise it.

    The legality of the emulator is not at issue in this lawsuit.

    The issue in this appeal is the validity of the method by which Bleem is advertising its product. In various advertising media, Bleem has included comparative "screen shots" of Sony PlayStation games.

    Later in the document:

    The veracity of the screen shots is not at issue in this appeal. Sony has not alleged that Bleem's depictions of the games played in different ways are inaccurate or misleading; it simply contends that Bleem may not use those screen shots because they are Sony's copyrighted material.

    Sony lost when it was concluded that the use of the screen shots constituted comparative advertising.


Generally speaking, just owning and using an emulator is completely legal in most places. (I won't say everywhere, because some places actually have strict laws about how any general purpose computing devices can be used.) But it also sort of depends what we mean by "emulator".

If we mean the sort of emulation software and systems we used to play with old software and ROMs then, as pointed out already, the legalities often centre on the intellectual property laws around that software or ROMs.

But it's not too much of a stretch to think of something like the Java "look and feel" as GUI emulation (Sun certainly did in some documentation). Microsoft also decided that emulating their UI in Java Swing was in conflict with their ownership of the UI.

Thus, emulation of the Windows look and feel in software created with Java and running in a JVM was restricted to VMs running on Windows. That is, the JVM disallowed apps from switching to the Windows look and feel at runtime if that JVM wasn't running in Windows. I admit this might be more of a trademark issue. But I think it highlights where things like rights and ownership sometimes take you.

Perhaps this is beyond the scope of the question, but it is often useful to be reminded that the law is simultaneously subtle and blunt sometimes, and decisions often turn on specifics of the language used.

I recall there was a very hackable programmable calculator platform that both emulation and writing your own apps for is essentially forbidden, and the rights holders are particularly litigious on both accounts. And they have used the "emulating our stuff is the same as using our stuff without permission" argument with some success. Well, where success is measured as "some courts have found in our favour" or "we scared away interested hackers and squelched further development."

Whether or not it is a good idea is another thing altogether.

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