Nintendo has successfully patented the emulation in software of handheld gaming devices, and the company has already begun challenging emulator developers to cough up royalties. Nintendo's patent, number 6,672,963, was filed in November 2000 but only granted on 6 January this year. It is titled 'Software implementation of a handheld video game hardware platform'.
The filing outlines a "software emulator for emulating a handheld video game platform on a low-capability target platform (eg. a seat-back display for airline or train use, a personal digital assistant, a cell phone)". It goes on to outline "a number of features and optimisations to provide high quality graphics and sound that nearly duplicates the game playing experience on the native platform."
News source: The Register