Nintendo's lawsuit makes extensive reference to the
Quickstart Guide that Yuzu provides on its own distribution site. That guide gives detailed instructions on how to "start playing commercial games" with Yuzu by
hacking your (older) Switch to dump decryption keys and/or game files. That guide also includes links to a number of external tools that directly break console and/or game encryption techniques.
Through these instructions, Nintendo argues, "the Yuzu developers brazenly acknowledge that using Yuzu necessitates hacking or breaking into a Nintendo Switch." Nintendo also points to a Yuzu Discord server where emulator developers and users discuss how to get copyrighted games running on the emulator, as well as publicly released telemetry data that shows the developers were aware of widespread use of their emulator for piracy (as the Yuzu devs wrote in June 2023, "Tears of the Kingdom is by far the most played game on Yuzu").