Auction property outstanding dues with housing society

One of the flat owner in our society purchased a flat in auction from a private bank after the first owner failed to pay the bank emis and interest. The second owner is not paying his outstanding dues after multiple phone calls and email exchanges. The previous managing committee of the society took a stand that they will not grant membership to the flat owner till the time he clears all the outstanding dues with interest on the flat (including one from the previous owner). In our society records we don't have any record of past communication done by the then Managing Committee(MC) with 1st/2nd owner of the flat pertaining to the demand of the dues or on any other matter. Neither we have any property papers (like Sale deed, NOC from Society etc. pertaining to the flat in our records). After the formation of new committee we started following up with the flat owner over phone call and email. We did not put a written request for clearence of outstanding sues to the flat owner till June this year. Meanwhile the said flat owner filed a complaint against the society to get membership of the society. The Dy. Registrar of the CIDCO ordered society managing committee to grant membership of the society to the flat owner. Now after this order when we sent him a written reminder via post (first one) to clear all the outstanding dues his answer is that the demand is unjustified and he will clear the dues only from the date he is granted membership of the society. He neither ready to submit any property papers for the society's records. Keeping in mind the Dy. Registrar Order and the stand taken by the flat owner what are legal options available with us. The New Managing committee is not ready to grant him membership (even after the order of Dy. Registrar) till the flat owner clears his outstanding dues entirely. Please guide.