One of the recent trends in modern international terrorism has been the ways that violent extremists have utilized online media, social media, and cyberspace. This poses ethical and political challenges to liberal democracies. On the one hand, they have a long and deep commitment to free speech. But on the other hand, they have obligations to ensure that the online environment is not exploited by violent extremism. This chapter draws from discussions of free speech to explain how and when particular sorts of constraints on public communications are justified. This chapter begins with a recognition that the norms of behaviour and free speech online are evolving, moves to an exploration of the key conceptual and ethical discussions around free speech, and then closes off with a set of framing questions to give some guidance as to how we can approach the question of whether online terrorist public communications should be restricted or not.