No S9s are so insignificant that's not a good defense against a situation like that from a hashrate standpoint. Though it would be interesting from a legal standpoint as mass noncompliance like that would make enforcement at a larger scale more difficult. It would also mean more people willing to sue the feds.

The best defense against a state actor messing with miners is geographic distribution of hashrate. Fortunately it's growing more distributed and will continue to do so.