If they do a good enough job with a propoganda campaign, they could make it so that you’re still liable unless you can prove that you sent them to a compliant custodian.

You would have to prove they didn't lose them. 

grayruby

…and arrest anyone who was unable or unwilling to surrender their private keys.

Jon_Hodl

Memes

Is The SBR A Threat To Self Custody?

It would be difficult to enforce. I suppose they could easily ban and enforce transfers out of kyc custodians like Coinbase to non custodial addresses but not sure how they enforce a ban on self custody. Even if they knew every person that held bitcoin in self custody they would need them to turn it over willingly or search their premises. 