This Essay traces the global spread of legal techniques that strive, as official government policy documents explain, to “push the border out” as far away from the actual territorial border as possible. This concept, enthusiastically embraced by governments worldwide, involves screening people “at the source” or origin of their journey, not the destination, and then again at every possible checkpoint along the way. My study is devoted to tracing the core countries and actors that have facilitated the adoption of such policies. I show that desired destination countries systematically learn from, and emulate, each other’s innovations in asylum-denying laws and policies. The lens of diffusion, which guides the analysis, emphasizes processes of inter-jurisdictional learning and emulation. It invites us to ask how and why “ideas travel” across jurisdictions and to trace the complex ways in which states are interacting with one another in shaping their own border control policies.