Nintendo Switch games are stored as encrypted data, and then decrypted at runtime by the console. Nintendo's legal position is that because the emulator will only run Switch games if the user provides decryption keys dumped from a Switch, it counts as a circumvention device and is therefore illegal to distribute. Nintendo sued Yuzu, one of the most popular Switch emulators, and the Yuzu authors chose to settle rather than going to trial.

Sounds like someone should take them to court.