EU digital identity law to make inter-EU signatures (And authentication) work.

As an example, an EU citizen working in Sweden should be able to submit Swedish tax forms whilst living here by using a digital identity from the originating nation.

There are also some standards in place like ETSI standardized extensions to PDF signatures so that you can verify that a signature inside the PDF was actually signed by a specific physical person (the standard is there but it's not fully used throughout the EU yet due to some legacies).

Implementation is a bit of a mess still but things are converging.

A mistake.

https://en.wikipedia.org/wiki/EIDAS

electronic IDentification, Authentication and trust Services