I don't know all the details around SSN, I wasnt born here. I didn't know you could opt out.But you don't have to get a SSN at birth. Sure it is a pain to avoid getting one but it can be done and is perfectly legal. I know a guy who is a Sovereign Citizen nutjob. He did not get SSN for either of his kids. They are around 7 and 4 give or take a year and as far as I know they still do not have SSNs.
But the point is, if they want to, they can implement it. It is nothing new.