To anyone who wasn’t sure, this is a flat-out lie by the Big N. It’s perfectly possible – and downright easy – to rip your own Melee disc and use the .iso that way. Takes about ten minutes and a Wii you can hack in five. And yes, hacking your own hardware and backing up the software you rightfully own is absolute, 100% legal. So in no way does Slippi “require” a pirated anything.
It is of course less straightforward to verify that your file came from one place and not another, and the distinction is so arbitrary that no one has ever bothered to make it. I’d love to see Nintendo’s reaction if TBH instituted a required “ripping your own copy” verification video or something, but it’s obviously too late for that now that the C&D is out.