CD/DVD Returns

CJLFC

I know the law states that if something isn't fit for purpose and hence faulty the buyer is legally entitled to a full refund, but does this applies to CD's too? I would've thought this may contradict copyright laws. If a "faulty" CD means the buyer is entitled to a refund, that means a crafty customer could buy a CD, take it home, rip it to their iPod or MP3, then take it back saying its faulty (knowing the store hasn't the facilities to test CDs) and get their money back, hence getting a CD for free. I've had customers decline an exchange saying they now don't want the CD which they bought, which sometimes seems a bit fishy to me, although sometimes understandable. Anyone know which law prevails?