Chapter 21 provides an account of the governing legal framework with respect to the gathering of digital evidence by US law enforcement authorities (LEAs) and the rules that bind US service providers – an issue that, given the quantity of data of interest in the hands of US-based providers, increasingly matters to LEAs around the world. It describes the general statutory and constitutional scheme governing data collection in the United States, with a focus on the federal level. It then examines specific questions with respect to cross-border cooperation, particularly in light of the Clarifying Lawful Overseas Use of Data (CLOUD) Act, which seeks to better facilitate cross-border access to data, in specified circumstances, and in accordance with baseline procedural and substantive protections. The chapter’s concluding thoughts point to both the need for more attention to cross-border access to data and some of the lacunae in US law.