First, resist the urge to go all vigilante crime-fighter.
While your intentions are good, only the person who holds the intellectual property rights (or someone acting on their behalf, like an attorney) can lodge a valid takedown notice under Redbubble policy and applicable law.
So why is the law set up this way? The rights holder is in the best position to identify what he or she considers infringing. There could be some fact that you don’t know about as to why the content owner did or didn’t file a complaint about a particular user’s work. For example, perhaps a license has been granted or the owner considers the work fair use.
Obligatory Yet Very Important Legal Disclaimer:
Don’t be fooled by any complicated jargon (and how snazzy we look in pinstripe). We are not your lawyer and this is not legal advice. We recommend contacting an attorney if you need an actual legal consultation.
Rather, this is general information aimed at giving you the legal lay of the land. While we can’t defend you in court, we know that art and IP ownership can be murky territory; the least we can do is arm you with the right kind of knowledge to get you started.