why would a country want to ban a nameserver, especialy one like sedo?
I have never heard of this problem. Perhaps you could just use another proxy on your browser, that should take care of it. Use a proxy server outside of China.
Or--
Use one of your own domains as a nameserver and forward it to ns1.sedoparking.com etc... and have your domains forward to your name server (which then takes them to sedo)