AbstractThe adoption of the Single Digital Gateway Regulation is a gamechanger in European e-government. For the first time, it creates a horizontal, non-sector specific legal framework for the direct exchange of digital evidence between public administrations in different Member States. However, these exchanges require public administrations to have a certain degree of trust in each other, which is built on a shared legal basis. The Single Digital Gateway Regulation achieves its goal of creating a legal basis and establishing trust, but also builds in a number of explicit and implicit legal constraints. These will help make the once-only principle in Europe a reality, but also enshrine limitations that will require revisions and expansions of the Regulation at some point in the future. This paper examines the genesis of the Regulation, its legal choices and priorities, the resulting implications and limitations, and potential challenges for the future.