This book is an introduction to the protection of historic properties by public agencies in three very different legal systems - the United States, the United Kingdom and Spain - as well as analysing international efforts to protect historic heritage. It is not intended as a comprehensive study of any of the legal systems, but rather as a tool to give the reader the chance to compare the legal techniques used in each different administrative system. The historical trends in each legal tradition are outlined, as well as present day regulation, using a multitude of examples of how historic buildings and heritage sites are protected in each country. While the publication is intended to cover legal mechanisms established to conserve all types of historic building, we will pay special attention to the protection given to industrial heritage, giving examples wherever possible of how a particular legal technique has been used to protect industrial buildings. We will also examine how case law has effected heritage protection, sometimes in unexpected ways.