Notwithstanding inherent differences between the counterterrorist financing regime and the regulatory regime governing communication service providers, there are clear benefits in taking lessons learnt from longstanding efforts on terrorist financing into account when developing a response to the online terrorist threat. Lawmakers developing a regulatory regime for communication service providers (CSPs) should engage with their counterparts involved in the response to terrorist financing to understand potential unintended consequences of this regime, including counterproductive incentives, risk displacement and other factors identified in this paper.