This book provides guidance for regulatory measures which enable the introduction of cognitive radio in the near future. These measures should be globally harmonised in order to allow the same principles and rules to be used with cognitive radio systems (CRS) around the world. Regulatory measures rely on the capabilities of CRS to detect and monitor spectrum in order to avoid existing usage. Based on this information CRS may operate, however, it should not cause harmful interference to existing usage. Regulation should take into account these requirements of shared use. There are a number of questions related to regulatory measures for the introduction of cognitive radio systems. These questions require comprehensive studies and field tests to verify proper functionality. In 2007 the radio communication conference of ITU (WRC-07) approved an agenda item for the conference of 2012 where the regulatory measures to introduce software defined radio and cognitive radio should be studied. The introduction of the CRS relies heavily on the results of WRC-12.