DE4A has been able to pioneer a multitude of e-government services in the past few years, also from a legal perspective. European legislation – including in relation to the once-only principle and privacy/data protection – has been one of the foundational inputs for DE4A, and as a result the project has learnt a lot about what the law allows and doesn’t allow. What exactly are the foundational legal principles, and how has DE4A implemented them? And perhaps equally important: how could European legislation evolve further in the future to enable even more effective and equitable digital public administration?