Historically, librarians and information professionals have professed and supported tenets of free thought and free access to all information. Guides, literature, conference sessions, and classroom exercises help guide LIS students and librarians through the provision of controversial materials. However, information professionals work within the political and practical boundaries of their institutions. They rely on imperfect and mediated technologies for access to information and communication. The reality is that such constraints, as well as external politics and broader societal and cultural challenges, can and do affect access to information. Librarians are thus limited in their impact by both internal and external factors. [complete abstract and full-text article]