How does it work, technically? In the US we have something that is supposed to be similar--put your number on a registry and telemarketers can't legally call you--but in practice we've just built a list of real phone numbers that telemarketers and scammers can use to target numbers that are owned by real people rather than brute-forcing the entire phone number space. If there is any enforcement at all, it's imperceptible.
Now it was decades ago I worked in cold calling telemarketing, but back then, the company basically purchased/subscribed to various lists of numbers they get from other companies, and also had lists of numbers to not call, either obtained from the do-not-call registries, or their own lists of "unsellable" customers, bad numbers and so on, simply crossed-references the ones that they for legal (or otherwise) shouldn't call, then the telemarketers who all sit in basically automated stations, end up just calling the "good" numbers. Different teams get different chunks of the numbers, but all the calls they're supposed to be doing, are supposed to not be on any of the do-not-call lists already.
The telemarketers themselves are told to basically hang up and mark the number as "do not call" if anyone picks up and says/mentions the name of lists. Most companies I knew from then took the lists seriously since their mechanism is based on actual laws in the countries, and evidently since I nor the people I enrolled in these lists receive marketing calls, the companies today takes them equally seriously.
I had to look it up, but it seems like you do a lookup per number before calling, and nixregistret will basically tell you if that number is in their register or not.
I'm not sure how enforcement works, from the copy on their website it seems like it's purely voluntary to even check there, but serious companies do because their customers will hate them forever if they call people who are registered.
I'm actually surprised it works so well given the apparent lack of enforcement. The only calls I ever get these days are from someone with an Indian accent who says "hello I'm calling from Blockchain", and even that has been a while!
