Earlier this month, the developers of Dolphin Emulator, one of the most prominent and beloved PC emulation simulators, announced that it would be coming to Steam. However, recently, they provided an update saying the Dolphin Emulator’s Steam release has been indefinitely postponed due to Nintendo issuing a cease and desist letter citing the DCMA against Dolphin’s Steam page. Now, Nintendo has offered an explanation.

According to the Dolphin Emulator devs, “We were notified by Valve that Nintendo has issued a cease and desist citing the DCMA against Dolphin’s Steam page, and have removed Dolphin from Steam until the matter is settled. We are currently investigating our options and will have a more in-depth response in the near future.”

In an email sent to Kotaku, the Mario and Zelda publisher said ““Nintendo is committed to protecting the hard work and creativity of video game engineers and developers. This emulator illegally circumvents Nintendo’s protection measures and runs illegal copies of games. Using illegal emulators or illegal copies of games harms development and ultimately stifles innovation. Nintendo respects the intellectual property rights of other companies, and in turn expects others to do the same.”

According to Nintendo, the Dolphin Emulator violates Nintendo’s intellectual property (IP) rights, including but not limited to its rights under the Digital Millennium Copyright Act (DCMA)’s Anti-Circumvention and AntiTrafficking provisions. The legal notice cites the anti-circumvention language of the DMCA and specifically claims that “the Dolphin emulator operates by incorporating these cryptographic keys without Nintendo’s authorization and decrypting the ROMs at or immediately before runtime. Thus, use of the Dolphin emulator unlawfully ‘circumvent[s] a technological measure that effectively controls access to a work protected under’ the Copyright Act.”

“I would characterize this NOT as a DMCA take down notice and instead as a warning shot that the software, Dolphin, if released on Steam would (in Nintendo’s view) violate the DMCA,” says attorney Kellen Voyer of Voyer Law, which specializes in intellectual property and technology law.

Talking with PC Gamer, Voyer said “Here, there is no allegation that Valve is currently hosting anything that infringes Nintendo’s copyright or, more broadly, violates the DMCA.  Rather, Nintendo is sending clear notice to Valve that it considers Dolphin to violate the DMCA and should it be released on Steam, Nintendo will likely take further action.  Given that Valve controls what is available on its store, it made the decision not to wade into any dispute between the Dolphin developers and Nintendo and, instead, followed Nintendo’s preemptive request and took down the Steam page.”