Emulators themselves are legal, but downloading the games (ROMs) isn't. Internet Archive How Safe Is the Internet Archive for Users? - AI Bud
However, custom firmware (like Atmosphere) bypasses that signature check, which is why NSP dumps are highly sought after by the console modding community. nsp archive.org
Are you looking to your own game backups, or explore what others have uploaded? Emulators themselves are legal, but downloading the games