The UK government fucked everyone over with Brexit, largely because they didn't care to think about the consequences.
Yes! A visa! Thank you! The strident heart and soul of the inhuman, inhumane, soulless bureaucracy. It is exactly like that.
This isn't exactly something to be lauded or celebrated! Have you ever dealt with having a visa? Have you ever been impacted by the uncertainty and confusion of the nation you are living in, changing its rules about your visa? Do you have any concept at all of the economic and the humanitarian impact of the bureaucracy's machinations around and involving visas? Even aside from the worst of that, have you ever abandoned a job and friends and the life you were trying to build somewhere, because someone changed the rules about visas? I liked that job, sir.
Oh, let me tell you about visas! I will tell you about them all day long. But, ah — I think it was a more flattering to the decision-makers when we were just talking about the cost of broken URLs and email addresses.
And then yes, like visa recognition agreements, if your country withdraws from a visa accord or economic region, the host country has no obligation to keep you credentialed, or domained. If unhappy about such thing, a more effective path is to activate compatriots against the withdrawal, rather than fuss at the host zone.
My friend, if these systems were just about aligning the incentives for workers and benefits and taxes, and otherwise tried to be understanding about human foibles, then people wouldn't point to immigration systems around the world as a Kafkaesque nightmare.
Just to pick an example — chosen for my familiarity, wholly outside of and unrelated to Brexit — the UK's Windrush scandal involved the bureaucracy actively destroying old records of immigration from British overseas possessions (particularly the Caribbean), then deciding years later to go after people who had been living in the country for decades — demanding they supply exhaustive documentation of their legal immigration, and their life and activities in the intervening time. Rest assured that this was a fully adversarial process! They did not offer to help anyone so affected gather these documents, or to make their case.
And later, in another unrelated scandal, the Home Office decided to react to an English-examination cheating scandal by analyzing everyone's examination results with some opaque computerized process, using the results to declare something like 97% of them as invalid cheaters — and sending nastygrams to about 9,700 university students, calling them dirty cheaters and demanding they leave country. Many of them did, and they forcibly removed others. Notably, they did not ask for them to re-sit the exam. They did not care about the lives ruined.
Of course the matter of the .eu domain is absolutely nothing compared to the daily nightmare that is "visas," but the same devotion to rules and insensitivity to the costs of policy runs through the matter. They could have grandfathered in existing domains, at least a little bit longer. I know that if I had a website and I had to move domains, I would want to run web and email forwarding for more than one year. If they wanted to be particular about just having the forwarding, they could have audited the sites to make sure that they were just redirects, and charged for the privilege. They didn't. There's no sane reason that couldn't happen except to preserve The Rules — but these rules simply are not a valuable end in and of themselves, despite the laud and honor they have received in this thread.
Funny how applying the eligibility the rules to you as they do to everyone else in the world who is not a member of the EU is seen as spiteful by you.
So I wish you all the best of luck as your continent, now deprived of the economic impulse of cheap Russian gas, discovers the true weight of its overbearing and inflexible regulatory state, and deindustrializes with a scale and speed never seen before in human history (already ArcelorMittal is importing iron from the US rust belt, of all places!!!). And I'm actually, legitimately, genuinely sorry for everything the populist backlash is going to do as things fall apart, because I expect it to be very ugly.
Visas are an imperfect tool for whatever they are designed to do, and any sufficiently advanced bureaucracy will develop ways to misuse such a gift.
They are a complete mess, especially so from the EU countries. US and UK have been more reasonable (no hard requirements of what documentation is needed, as long as you can prove that you are travelling with an actual purpose, and once granted, it's for at least 6 months for UK or 3 years in case of the US), but luckily we've entered the Schengen whitelist since.
Ah yes. Because the UK isn't planning on sending refugees in Rwanda. /s