[OstiaAntica]

You can't copyright or trademark a fashion pattern, like your friend's jeans.

Fake products using a trademarked name is a different matter-- they are of inferior quality, and widespread distribution seriously damages the legitimate brand.

[electromagnetic]

Yes, the name ripping is their right to enforce, however the big brands also prevent knockoffs and imitations from being sold in major stores for threat of pulling everything with their name on it if the store stocks similar-look products.