It has nothing to do with any UN jurisdiction at all. International law allows for the arrest by any government of someone wanted for "crimes against humanity." The British arrested former Chilean dictator Augusto Pinochet several years ago when he was in the UK for medical treatment. There is also an outstanding warrant for Henry Kissinger in France (and, I think, a couple of other countries as well) on the same grounds. Maybe doing this for aiding and abetting child molestation isn't possible, maybe it is. Personally, I think the Brits should test it.