When it comes to emulation, Nintendo has a long history of going after the websites that distribute copyrighted game ROMs and some of the modders that make piracy-enabling hardware. But Nintendo’s legal takedown efforts have generally stayed away from emulation software itself.

This weekend saw an exception to that rule, though, as Nintendo’s lawyers formally asked Valve to cut off the planned Steam release of Wii and Gamecube emulator Dolphin. In a letter addressed to the Valve Legal Department (a copy of which was provided to Ars by the Dolphin Team), an attorney representing Nintendo of America requests that Valve take down Dolphin’s “coming soon” Steam store page (which originally went up in March) and “ensure the emulator does not release on the Steam store moving forward.” The letter exerts the company’s “rights under the Digital Millennium Copyright Act (DMCA)’s Anti-Circumvention and Anti-Trafficking provisions,” even though it doesn’t take the form of a formal DMCA takedown request.

In fighting a decision like this, an emulator maker would usually be able to point to some robust legal precedents that protect emulation software as a general concept. But legal experts that spoke to Ars said that Nintendo’s argument here might actually get around those precedents and present some legitimate legal problems for the Dolphin Team.

The Dolphin difference

For the most part, using reverse-engineering techniques to emulate one piece of hardware on another piece of hardware is protected under US law. For some gaming platforms, though, emulator-makers can run into potential legal liability when implementing a system’s BIOS—the piece of copyrighted code that controls the Basic Input/Output System.

In a seminal 2000 decision surrounding Connectix’s Virtual Game Station emulator, the 9th District Circuit Court ruled that copying that BIOS for the purposes of reverse-engineering “is protected as a fair use.” But even if an emulator maker can’t reverse-engineer a complicated BIOS, it can usually get around legal liability by asking users to bring their own BIOS file for the emulator to point to. Since the emulator itself doesn’t include a copy of that crucial copyrighted BIOS software, it can generally be freely distributed without much legal risk.

Unfortunately for the makers of Dolphin, those legal protections probably don’t help much in this case. That’s because Dolphin’s public source code includes a leaked copy of the Wii Common Key, which is a crucial part of decrypting the encrypted content on a Wii game disc. And it’s that decryption key that Nintendo seems to be focusing on as a potential DMCA violation in its letter to Valve.

“Wii and Nintendo GameCube game files, or ROMs, are encrypted using proprietary cryptographic keys,” Nintendo’s lawyers write. “The Dolphin emulator operates by incorporating these cryptographic keys without Nintendo’s authorization and decrypting the ROMs at or immediately before runtime.” That means the emulator “circumvent[s] a technological measure that effectively controls access” in violation of the DMCA, the lawyers write, meaning distribution of the emulator itself “constitutes unlawful ‘traffic[king] in a technology … primarily designed or produced for the purpose of circumventing a technological measure.'”

“We do not deny that the Wii common key is embedded in the Dolphin source code,” a Dolphin Team representative told Ars Technica via email. “We have no further comment at this time while we consult with an attorney.”

“It is with much disappointment that we have to announce that the Dolphin on Steam release has been indefinitely postponed,” the team added in a weekend blog post. “We are currently investigating our options and will have a more in-depth response in the near future.”

https://arstechnica.com/?p=1943266