Well, after reading that ruling I'm not sure what power the registrar does have, if any. Whoever takes it should have a lot of questions before proceeding.
The RG's power is to follow the law as clarified by the Court and deregister voters providing A) a six month period has elapsed and B) three federal elections have been missed. I'm very disappointed that Homely is resigning over this particularly since all three of us knew that he had only the best of intentions in following the law as he interpreted it but I think the ruling makes it clear that the discretion available to the office of RG is very limited, particularly when it comes to something as significant as removing voters.