There are legal problems when creating emulators, sure people work hard to avoid them, but I don't think they should have to do that in those cases, so I specifically wrote "all emulators" should be legal. For example, Dolphin to work requires cryptographic keys that technically belong to Nintendo, so they may be sued for providing them. Some emulators require you to find bios on your own because they can't legally provide them, and their emulator doesn't work without it.