Nintendo's aggressive stance against emulation is well-documented. The company's legal actions have resulted in significant settlements and the cessation of development for several popular emulators, including Yuzu and Ryujinx. The case against Gary Bowser, involving the resale of devices that bypassed Nintendo Switch security measures, resulted in a substantial financial penalty.

A recent report from Denfaminicogamer, via VGC, sheds light on Nintendo's legal strategy. Koji Nishiura, a patent attorney and Assistant Manager of Nintendo's Intellectual Property Division, clarified that while emulators themselves aren't inherently illegal, their use can become illegal depending on how they interact with copyrighted software. Specifically, emulators that copy game programs or disable console security mechanisms may infringe on copyright laws.

This is primarily based on Japan's Unfair Competition Prevention Act (UCPA), which limits Nintendo's reach outside of Japan. The R4 card for the Nintendo DS, which allowed users to play pirated games, serves as a key example. Nintendo successfully argued that its sale violated the UCPA, leading to its ban in 2009.

Nishiura also highlighted the illegality of tools that facilitate the download of pirated software within emulators, citing examples like the 3DS's "Freeshop" and the Switch's "Tinfoil." Nintendo's lawsuit against Yuzu highlighted the alleged piracy of The Legend of Zelda: Tears of the Kingdom one million times, linking the emulator's Patreon funding to the distribution of pirated content.