That will just lead to situations where one company scrapes the site, cleans the content of tags, and sells the data, and another does the training on the precleaned data. The first one hasn't trained and the second one never saw the tag.
This isn't a new concept in law. It's similar to buying goods that were stolen or procured through illegal means. Here's the US law that applies when it happens across state lines:
Note that it requires the defendant to know the goods were illegally taken. Can be hard to prove, but not impossible for companies with email trails. The fun question is, what will the analog be for the government confiscating the illegally "taken" data? A guarantee of deletion and requirement to retrain the model from scratch?
