If it was the gov't directing a registrar to seize a domain name, that's pretty clearly a violation of the first amendment.
If a registrar seized a domain name, that wouldn't be a first amendment per se, but it would probably be a breach of contract and should be illegal one way or another.
And then there's some grey areas with copyright that I think have been hammered out in courts… IANAL
If it was the gov't directing a registrar to seize a domain name, that's pretty clearly a violation of the first amendment.
If a registrar seized a domain name, that wouldn't be a first amendment per se, but it would probably be a breach of contract and should be illegal one way or another.
And then there's some grey areas with copyright that I think have been hammered out in courts… IANAL