A private company has no power to "require" a customer provide something that does not exist, or that would not be available to them. This of course applies to UK licenced casinos accepting UK players. Players also have legal protection against "Unfair business practices" and also must be "treated fairly" by any business.
Confiscating a win (having accepted all the prior deposits and losses) would not be seen as the customer being "treated fairly" if there was an inflexible approach that made it impossible for the player to meet what is required of them.
The banks have already been rapped over the knuckles over the issue of too strict a requirement for documentation as it meant significant numbers of people were "financially excluded" from having a main stream bank account simply because they didn't drive nor travel. The electronic checking works so well because it has to stand in lieu of a national ID card, and of course needs to be fit for purpose.
However, it does rely on the player making sure they register for the electoral roll, which unlike driving or travelling abroad, is actually a legal requirement, and theoretically one can be fined £1000 for not registering on the electoral roll.
The ONLY approximation we have for an ID card, one that is purely a proof of ID and age, rather than a licence to drive or a travel document, are the privately issued "citizen cards". They are primarily used as "proof of age", but obviously need a photo of the holder to compare with the person using it when buying that bottle of White Lightning paint stripper at the local convenience store.
It's mainly because a significant number of adults aspire to drive that most players are able to send in their driving licence as their "National ID card", however not everyone can drive, and a significant minority can never drive due to their medical conditions. They can't even get a provisional (without failing to declare on the application form) in order to please a casino.
When dealing with a UK player, casinos should look at the rules governing their UK licence, and if they conflict with a licence from, say, Malta, then the UK rules should predominate.
It's fine for a country that issues ID cards to all adult citizens to say that it's safe to say that anyone who can't present one is "dodgy", but this assumption does not apply in the UK.
Passports are not compulsory, and if the EU had it's way over the UK, many more British players wouldn't have one. I would expect many European players only bother getting a passport if they intend to leave the EU, but of course they have ID cards, so it's not an issue casinos will have become aware of.
In the end, a UK player can as a last resort get a passport, but if it's their first one, it can take many weeks, and involves a personal interview at a passport centre. Given that it's such an ordeal, it's hardly surprising that many UK players resent the fact that a casino has been more than happy to accept lost deposits for months, if not years, but then suddenly insists they go to all this effort to get a passport when they win because nothing else is good enough. No player wants to have their life changing win on hold for a couple of months whilst they obtain their passport when there has been no such problems in other aspects of their financial lives, to which the SAME anti money laundering laws apply as apply to casinos.
Ironically, casinos even go out of their way to cater for players who don't hold a bank account, the financially excluded, by offering things like the former UKash and now Paysafe voucher system, even PREFERRING such options in a few cases, yet these are the same players who are least likely to ever be able to provide "photo ID", which is WHY they have to resort to things like UKash vouchers for all their online payments - they can't get a bank account, let alone a card.
Regulated online casinos have only just been introduced into the UK, before that it was a free for all, up to us where we played, and the government would neither interfere nor protect us, nor make any tax revenue from the activity. If the problem of "financial exclusion" becomes an issue with UK facing casinos due to their insistence that the UK government should have issued ID cards in order to make the rules work properly, the casinos can expect the same rap over the knuckles felt by the banks, and will be told to use electronic checks in the main, and supplement these with documents that ARE issued to UK citizens, and in the combinations proscribed on the lists used by the banks for verifying customers. These lists provide for the fact that some customers will neither drive nor travel, and will ONLY have the "paper" documents from official sources.
There is a suspicion that casinos are not always playing fair with UK players because they have to PAY for conducting these electronic verification checks, but it's FREE to source the passports and driving licences direct from the player, so there is only the costs involved with internal verification.
One sign that casinos need to adjust to the UK way of doing things is all the complaints that have been upheld by the ASA over the "industry standard" methods of advertising bonuses and other promotions on websites and via email. These were "misleading" by design due to the fact that they needed to be "click bait", but this falls foul of advertising rules in the UK, where "click bait" isn't allowed if it gives a misleading impression of the offer as a whole that can only be seen once someone has clicked through. The ASA expects negative aspects to be given "equal prominence" as the positive aspects, which pretty much renders the standard "£1100 free - keep what you win" free spins offers that came for many Microgaming casinos unlawful in the UK, which is probably why I don't see them so much for UK facing casinos. Where I do, a ruling from the ASA is likely to follow.
It's good to see that many of the UK facing casinos ARE moving over to electronic verification, however this can have the unintended effect of lulling UK players into a false sense of security, with those who don't drive or travel at risk of receiving a VERY nasty shock one day should they hit an exceptional win, or are marked for a random enhanced verification check.