European Telecommunications Standards Institute (ETSI), Lawful Interception (LI); Retained Data; Requirements of Law Enforcement Agencies for Handling Retained Data (ETSI TS 102 656 V1.2.1 (2008-12) (2008) (full-text).
The present document gives guidance for the delivery and associated issues of retained data of telecommunications and subscribers. It provides a set of requirements relating to handover interfaces for the retained traffic data and subscriber data by law enforcement and other authorized requesting authorities. The requirements are to support the implementation of Directive 2006/24/EC of the European Parliament and of the Council of 15 March 2006 on the retention of data.
Not all requirements necessarily apply in one individual nation.