If you’re a single person wearing a Batman costume to San Diego Comic-Con, your use is almost certainly non-commercial and you are not liable for copyright infringement. But if you’re a business who specializes in making these costumes, the question becomes a bit more problematic. On its face, it’s easy to assume that it would constitute infringement. After all, DC Comics owns the character of Batman and his general look. If you were to visit your average costume shop looking for a Batman cowl to wear at Halloween, every single one of them would have “officially licensed product” printed on a tag somewhere. No costume designer wants to tempt fate by producing unlicensed Batman merch even if they could get away with it. That’s the smart move.