Is there a law against taking photos at a concert or sports event and selling them?
I don't know either way. I'd normally be with kragen on this, but... I have become cynical enough that I wouldn't be surprised if the sports leagues had gotten laws passed about it.
Does anyone know?
There are laws around photography in public spaces, usually around being a pain in the ass and harassment or malice, but in a private space it’s up to the entity controlling the space.
probably if you violate those conditions of entry, what you're facing is a suit for damages for breach of contract. if you uploaded your photos to wikipedia that doesn't make the wikimedia foundation liable the way they would be if there was a copyright being violated or an invasion of privacy, so the breach of contract suit may not be very useful to the plaintiff
they're working on it: https://www.wipo.int/podcasts/en/ip-matters/transcripts/ip-m...