Well, it is "illegal" when you play the original disc in another system than what it's meant to be played on. Even if you use a backup.
But we are not playing here
There's no piracy involved anyway, you are not exactly infringing copyrights of the media, but actually the gamecube itself. I don't know what to call that, but probably if shit hits the fan on a big scale, Big N can say they lost income on sales of gamcubes due to people being able to play the games on another system. That's the "illegal" part.
But this is something different, I see the emulation community as something educational, and we use it also that way... Sometimes people mistake Dolphin with commercial or other software, but it's purpose is different.
So educate yourself, and njoy what you learn and know that this is not a way to be able to "play" GC games on pc, but it's a gateway that interpets software in a totally different way....And I must say, I like the possabilities.
Just one side note before I start to help this thread, and I'd like not to get in a discussion about this one BUT:
--Owning the game that you made a backup from doesn't matter, if we are talking about emulation: No GC involved nor do you ever "play" your backup.
--Not owning a game but deleting it after 24hrs is pure cr@p. I've never seen so many disclaimers on R0m sites since one guy thought of this one. Nowhere on the planet there's a written law for this. People just copy eachother, that's it.
So, all "legal" stuff aside, if you don't own a gamecube (no exploit possability) nor a >DVD< drive, then you are not able to load the medium onto your pc. And that means....yeah.
Making a backup at a friend's house is illegal, just kidding, it's doable.
Peace,
Nepsi.