Maybe they can do that, but that would require piercing corporate veil first which is costly. JoeSchmoeLLC is probably judgement proof. Any attempt to force it to comply would cost a boat load of money.

However, it is a lot more likely that the LLC is owned by those with no nexus to Europe it is extremely unlikely that EU can do anything to punish this company. Hell 99% of web forums have European users.

Maybe it will have teeth against Google/Facebook/Tinder/Match/etc because those companies actually have assets in Europe but it won't be effective against companies with no nexus.