Originally Posted by MonoLoco
Roms are illegal regardless of whether you own the game or not; those disclaimers you see at the top of rom sites saying that ownership makes it legal are just to keep you coming back. That being said, you would probably never get caught, and pirating a game you already own isn't exactly something anyone's going to care about.
The thing is, using that line of logic, what's the difference if you're stealing intellectual property or modifying it...both are illegal, and you likely wouldn't get caught doing either. If you've ever been to a rom site, you'd see there are tons of hacks of pretty much every major commercial release, and I don't see Nintendo showing up at their doors with cease-and-desist letters.