Emulators don't violate IP on games. It may violate IP on the hardware, but I doubt that as it was all created from clean scratch.
If Nintendo would go after sites offering pirated ROMs I can fully understand that. But going after emulators, or companies that happen to sell a product for which emulators are available, is just not leading anywhere. Nintendo is IMHO happy to finally having found a company behind emulators for the first time. That's why they love to sue Nokia.