for sure!

in my comment, i was speaking more generally than i should have, and that (obviously, in hindsight) caused some confusion between the specific case of the hypothetical company, and the general case of an employer providing a negative reference. my bad -- and it is too late to edit to provide clarification.

No problem, I wasn't very clear either! I remember someone I know looking into this in the early 2000s as part of a wider collective thing. It's long enough ago that I can't remember the details but it was definitely less about a poor reference and more about the individuals' being on a list somewhere without having even applied for a job. And come to think of it, it's probably even more illegal now because of GDPR.