This report contributes to the ongoing national security debate in Canada by providing an analysis of the proposed Communications Security Establishment Act, a major component of the reforms set out by the Government of Canada in Bill C-59 (An Act respecting national security matters). The proposed CSE Act will furnish Canada's foreign signals intelligence agency with a comprehensive new legal framework. In the course of this analysis, we summarize the CSE's proposed mandate, activities, operations, and powers, with an emphasis on their potential implications for human rights and global security. We undertake a detailed analysis of key issues related to the CSE arising from Bill C-59, including a study of the Establishment's changing mandate; problems of review, oversight, and independent control; exceptions to the general rule against directing activities at Canadians and persons in Canada; tensions between aspects of the mandate; the need for a formal vulnerabilities equities process; and issues arising from arrangements with foreign and international bodies. We also offer a series of over 50 recommendations which, if adopted, would provide a more legally sound framework for the CSE, better protect global security interests in a rapidly changing technological environment, and more effectively account for Canada's domestic and international human rights obligations. In particular, we make recommendations to improve systems of review, oversight, and control of the CSE and to constrain the CSE's ability to engage in activities that are problematic, abusive, unconstitutional, or in violation of international human rights norms.