Yeah, Spain went this route. We used to get telemarketing calls from random mobile phone numbers (or straight up "hidden" number), so was hard to really know where they came from, unless the person admitted it in the phone call. A year or so that was made illegal, and now every "unwanted telemarketing" call has to come from a landline with a regional code, or the toll-free numbers, which leads to them actually having to register first, so easier to crack down on the ones that don't follow the "anti-spam" lists like Lista Robinson and similar, or break the rules in other ways.