The solid legal theory behind Nintendo’s new emulator takedown effort

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."

On the merits

Nintendo's argument was clearly strong enough for Valve, which took down the Dolphin Steam page (archived here) after receiving the letter Friday. And while Nintendo's letter falls short of an "official" DMCA takedown notice (much less an actual legal case against Valve or the Dolphin Team), the Steam Terms of Service means Valve is well within its rights to take down pretty much any store page for any reason.

"Due to the IP complaint, we have removed Dolphin Emulator from Steam unless and until both parties notify us that the dispute is resolved," Valve said in an email sent to the Dolphin Team and shared with Ars Technica (Valve did not reply to a request for additional comment).

Valve aside, if Nintendo actually wanted to take this to court, lawyers who spoke to Ars said they might have a decent case. "I think Nintendo has a legitimate—if untested—argument that the encryption keys violate the anti-circumvention provision of DMCA," attorney and digital media specialist Jon Loiterman told Ars. "If they're including the Wii common key in the files, then maybe there's an argument that it goes further on an anti-circumvention front," attorney Mark Methenitis added.

But a potential court case wouldn't necessarily be a slam dunk for Nintendo, either. The Dolphin developers could make the "untested argument... that the use of the encryption key in Dolphin isn't a circumvention mechanism and is more like the BIOS to the extent that it is 'necessary to access unprotected functional elements,'" Loiterman said.

"The technical details of precisely how the key is used in Dolphin would make a big difference here," Loiterman continued. "If it went to court, it would likely turn on other DMCA anti-circumvention precedents that have nothing to do with emulators."

Even if that argument didn't work, the Dolphin Team might be able to use a "bring your own BIOS"-style workaround to continue distributing their emulator legally. "Simply releasing the emulator and saying 'you need to insert the common key yourself' would potentially defeat the claim, and the Wii common key is pretty easy to come by," Methenitis said. That said, "it could be possible for Nintendo to argue that the systems within Dolphin that use the key are still 'circumvention' even if you take out the key," Loiterman said. "It would depend on the technical details."

Regardless of that legal argument, removing the key from the Dolphin source code "would also put Valve in a stronger position to say they're not hosting or distributing the offending material," Loiterman said. But that might not be enough for Valve to want to insert itself into a potentially fractious legal debate. If it came to it, "Valve may simply not be interested in picking that fight with Nintendo on behalf of the Dolphin team," Methenitis said.