Mr Assange (founder of Wikileaks) has been arrested under a European Arrest Warrant (EAW) issued by Sweden - see BBC 8th December 2010. The EAW refers to sexual offences alleged to have been committed in Sweden.
Earlier this year, Law and Lawyers looked at the European Arrest Warrant and at the expanding influence of the EU in relation to criminal matters - see Ever Expanding Influence No. 1 ............ No. 2 and ............. No. 3
The Head of Legal Blog carries an item on the Assange case. See also the UK Human Rights Blog.