Banning exchanges could be accomplished. Most would see it as a nuclear option though. It seems more probable that some form of key registration will be used to control the currency flow. 

 So, KYC of your key 

 If your coin isn't kyc'ed then you are a money laundering criminal. Eventually, all coins will be on a whitelist if more and more people start complying. KYC coin is a dystopian future.