Under the US Constitution personal freedom trumps national security. Or rather it's supposed to. It's been all bass ackwards in that regard for the last 13 years or so. Even so I don't see any case for banning crypto based on *insert alphabet soup agency here*'s ability to snoop impressing the SCOTUS, nor do I see any such law having a prayer of avoiding getting the scrutiny of the SCOTUS justices.
Then again the current batch of SCOTUS justices have made some really quite brain-dead rulings in direct contradiction of what the Constitution says in the past so who knows.