Playing a digital backup (WAD-style) actually offers superior performance to the original disc:

A forwarder does not contain the game itself. You must already have the Mario Kart Wii format) stored on a USB drive or SD card. 2. Download the Files WAD Manager: Download a reliable installer like YAWM ModMii Edition or another WAD manager from the Wii Hacks Guide Forwarder WAD:

This is the most critical section. The legality of downloading a WAD or WBFS file hinges entirely on your ownership of the original game.