If the regulators wouldn't know it is unenforceable, they would have banned it with these regulations. Instead, these new laws are the toughest they can actually enforce. Alreads at the cost of having created a one way street where regulated 'crypto assets' can only flow out, but never back in. It means these regulations don't stand on principles and are only a temporary measure.
They can't stop Bitcoin transactions and they know it. If they were to try, they fail and instead of regulating anything, they would have the given the best possible advertisement to Bitcoin and outlined their realm of power. Bitcoin is above and beyond their influence. The emperor has no cloths etc..
It's the 12 words line they can't cross.
I sincerely hope they do, though.