The European Court of Justice has ruled that EU countries do not have to force ISPs to reveal the names of users associated with IP addresses in civil copyright cases. The court said: "Community law does not require the member states, in order to ensure the effective protection of copyright, to lay down an obligation to disclose personal data in the context of civil proceedings."
Read more about it at "EU Court Says File Sharers Don't Have to be Named" and "Mixed Reaction to EU Court Ruling on Copyright."