It can indeed be complex. It depends on what type of law it is, in this case it’s a regulation so there is no need for countries to ratify it:

Regulations

Regulations are legal acts that apply automatically and uniformly to all EU countries as soon as they enter into force, without needing to be transposed into national law. They are binding in their entirety on all EU countries.

https://commission.europa.eu/law/law-making-process/types-eu-law_en

I think you can just search for the https url directly since both Mastodon and Lemmy have WebFinger support.

Doesn’t this apply regardless of whether the owner is the government or a private organization? All types of owners have their pros and cons, so I’d prefer a healthy mix so that users can pick the one they prefer.

There is also a need for governments to setup their own instances for their employees and institutions to avoid them having to sign up to a third party service if their work involves communicating on the fediverse, which also makes it clear that messages sent from this instance are official government communication (like governments have done with email for a long time). That’s how the EU’s Mastodon instance is setup: https://social.network.europa.eu/about