Math nor encryption will be outlawed. They will demand that all communication platforms provide lawfull intercept facilities to the authorities. Parties that do not comply will be fined or forbidden.
Don't be fooled that it won't work. It works in China and they have math there too.
It will work just fine, they'll get a ton more traffic to analyze. But it won't work for the goal that they claim to have, it won't make a dent in crime (which China has plenty of, at all levels), and it won't stop terrorism (which China also has plenty of, and which of course others would label as freedom fighters).
The only thing China will succeed in is extending the gerontocracy for a little bit longer. But eventually the cost of strongly encrypted communications will drop to zero and then the information advantage that the government has is over.
Think 'Starlink' + a couple of rounds of tech improvement and the GFOC might as well not exist. The question is will the people care? In China, I'm not so sure. In the West, maybe they will, maybe they won't, but I for one will be happy to utterly ignore this if it ever makes it into law. Right now I don't bother encrypting my mail, but if this happens I might drop off the grid entirely, and I'll make it my mission to spread strong crypto as far and as wide as I can.
But for now it's just a misguided proposal by a clueless bunch of bureaucrats.
Don't be fooled that it won't work. It works in China and they have math there too.