Nintendo claims that Tears of the Kingdom was pirated 1 million times.
The blue and red logo for the Yuzu emulator.

Nintendo has filed a lawsuit against the makers of the Yuzu emulator, Tropic Haze. In their filing, made February 26, Nintendo says that Trophic Haze knowingly and willingly let people pirate The Legend of Zelda: Tears of the Kingdom over one million times over a week before the game was officially released to the public.

Nintendo filed the lawsuit in the US District Court of Rhode Island. In the suit, Nintendo claims that the Yuzu emulation software "unlawfully circumvents" technologies within the Nintendo Switch console and Switch software (games). Nintendo says that these bypasses are done in Yuzu through "illegally-obtained" copies of keys that are usually stored on the Switch console itself. These keys were allegedly distributed through a variety of piracy websites, which would-be pirates could obtain to allow them to play pirated Switch games on Yuzu.

Nintendo claims that Yuzu aided in the piracy and distribution of The Legend of Zelda: Tears of the Kingdom. They say that the Yuzu website offered detailed instructions on how to install the game. Nintendo's suit blames Trophic Haze for "unauthorized reproduction and distribution of protected works" along with several other claims.

In effect, Yuzu turns general computing devices into tools for massive intellectual property infringement of Nintendo and others’ copyrighted works. […] Today, Yuzu provides any Internet user in the world with the means to unlawfully decrypt and play virtually any Nintendo Switch game—including Nintendo’s current generation and most popular games—without ever paying a dime for a Nintendo console or for that game. And to be clear, there is no lawful way to use Yuzu to play Nintendo Switch games, including because it must decrypt the games’ encryption. Defendant must be held accountable for willfully providing users the means to violate Nintendo’s intellectual property rights at such a scale. The harm to Nintendo is manifest and irreparable.
Nintendo is seeking $150,000 in damages, plus additional damages and profits Trophic Haze made from these alleged violations. The profits in question mostly stem from the Yuzu Patreon, which is currently pulling in over $30,000 per month. This figure rose significantly in the weeks during and immediately after Tears of the Kingdom began to be pirated. Nintendo is also demanding that Trophic Haze stand trial.

This lawsuit is certainly a tricky one. Emulation itself is not inherently illegal. However, if it's discovered that Yuzu directly profited or aided in the distribution of the pirated version of Tears of the Kingdom, they won't have much of a leg to stand on legally. These sorts of things will be found during the discovery phase of this trial, if it comes to that. Publicly, Yuzu and Trophic Haze did not seem to directly distribute access or links to the Switch decryption keys nor did they seem to provide direct access to the pirated version of Tears of the Kingdom.