Hehe, thanks.
I don't think its illiegal though. I mean if you overclock it sensibly, and it broke just from standard use, and something was actually wrong with the card afterwards (not caused by overclocking), then why shouldn't you be able to replace it? Who says the overclocking did it, when it might not have been?
I guess if you've overclocked it stupidly, there might be burn marks, etc or something, but sensible overclocking wouldn't do that, and it could just die anyway.
Overclocking though is proven safe if done in that way. As long as you hjave knowledge in it, nothings wrong.