There has been intense interest in the proposals to implement Article 23, both in Hong Kong and abroad. This book will be valuable to anyone who has followed or participated in that debate or has an interest in the delicate balance between civil liberties and national security. The book will be particularly useful for legislators, policy-makers, lawyers, journalists, historians, teachers, and students, especially in the fields of law and the social sciences. The statutory Appendix will assist teachers and students to draw comparisons between existing law and the government’s proposals. In 2003 more than 500,000 people marched in Hong Kong against the National Security (Legislative Provisions) Bill, which would have prohibited treason, sedition, secession, and subversion against the national government of China and included new mechanisms for proscribing political organisations. This edited collection analyses that legislation, particularly the implications for civil liberties and the one country two systems model. Although the massive protest compelled the Hong Kong government to withdraw the Bill from the legislature in 2003, it will likely propose similar legislation in the future because Hong Kong has a constitutional obligation to implement Article 23 of the Basic Law. The book provides detailed and balanced commentary on the Bill, explains why certain proposals proved so controversial, and offers concrete recommendations on how to improve the proposals before the next legislative exercise.