In 2018 every leader in Europe read Mariana Mazzucato‘s The Entrepreneurial State and then collectively wiped it from their memories.

The “build, not buy” point is right, but only for core mission software: the systems an agency’s actual purpose depends on. If that capability is bought from a foreign vendor, the agency is effectively renting its own muscle.

For everything else, building in-house is not sovereignty. It is usually waste. Agencies should not be writing their own analytics tools, email servers, or generic back-office software just to feel independent.

That layer should be bought, but bought carefully: European or open-source where possible, with open formats, export rights, and the ability to fork or self-host if the vendor changes direction.

So it is not one rule. It is two layers: build the software that is your core capability, and procure the rest in a way that avoids lock-in. Both are part of keeping capability in Europe.