How the fuck could a law like that possibly be enforceable? Mozilla should just tell them to go fuck themselves, offer alternative IPs so people can get around country-wide DNS blocks, and then go about their day. Who cares what some spineless country wants?
That's what's happened in other countries that have tried to implement this. Unless you want to basically go the Chinese route and ban all exterior access it's an utterly unenforceable law. Which I am sure they would have been told if they had bothered to consult anybody with domain knowledge.