You can however disallow Google from indexing your content using robots.txt a met tag in the HTML or an HTTP header.
Or you can ask Google to remove it from their indexes.
Your content will disappear from then on.
You can't un-train what's already been trained.
You can't disallow scraping for training.
The damage is already done and it's irreversible.
It's like trying to unbomb Hiroshima.
That might be a good way to go about it
Can probably do all that well-enough (probably doesn't need to be perfect) by leaning on FAANG, with or without legislation.
But: opt-in by default, or opt-out by default?