At this point very few client resolvers check DNSSEC, so something that stripped off all the DNSSEC stuff and inserted lies where required would "work" for most clients. At least until they realized they couldn't get to PokerStars and switched their DNS to 8.8.8.8.
If the ISPs don’t start blocking well known public resolvers or even just blocking port 53 in general (which has been known to happen).
I doubt the ISPs in Québec would have much sympathy for this proposed law. It makes their life harder and provides them no benefit. Should it pass (remember, it's just proposed), I expect they'd just adjust their DNS caches to block responses for the list of domains that the government mails them and claim they're in full compliance. R's, John