Couldn't an emulator use a module as the core, and leave it up to the user to find the 'illegal' emulator core and use it? Kind of like how you need a copyright

Couldn't an emulator use a module as the core, and leave it up to the user to find the 'illegal' emulator core and use it? Kind of like how you need a copyrighted BIOS or ROM to use certain emulators, but of course those files can't be distributed with the emulator.