Yes they can demand them, theres two acts they use to gain this but I'm not 100% if they are only regarding UK laws, hosted sites, etc
This site is setup in the states, I'm not sure on the laws and the affect other countries can have, when individual countries laws are involved..
Its the second time they have contacted me, they did earlier in the year concerning images posted with threatening comments...
So just be cautious when posting anything blatant, this goes for posts and members on other websites too...