This paper analyzes changes to the definitions of "authorized users" contained in electronic resources licenses and embedded in access control technologies from the mid-1990s to the present. In analyzing changes to the license and technology-based definitions, it tracks shifts in major stakeholders' perceptions of authorized users and describes developments in licensing and access control technologies. The paper demonstrates that the concept of authorized users has been shaped by a mix of social and technical elements, including changes to information providers' and libraries' business models and missions, shifts in norms for license terms, and development of technological tools used to facilitate or constrain access.