http://www.wipo.int/treaties/en/ip/rome/summary_rome.html
wikimedia itself observes that shoting without a permit may put you in breach of a contract you signed when you purchased the ticket, as I alluded to above:
http://commons.wikimedia.org/wiki/Commons:Copyright_rules_by...
...which is why publishers won't buy photographs without a signed release, such as this one:
http://images.tbd.com/entertainment/gaga-release.pdf