Mr Downer began signing certificates in 2002, barring Falun Gong protesters from displaying large banners and using loudspeakers outside the Chinese embassy in the capital.
The certificates were issued under regulations protecting the foreign missions in Auastralia.
Earlier this year the Australian Capital Territory Supreme Court ruled the certificates were invalid.
But the Falun Gong group is pursuing further legal action, because it is still concerned Mr Downer could resume issuing the certificates, and wants them banned entirely.