Recovery of maintenance amount from a non co-operating flat owner

Dear Experts, Need a guidance on the below: We are an apartment association registered with Registrar of Society, Karnataka. There are in total 38 flats in the apartment. One of the flat owners is very rude and they have moved in to the flat without obtaining an NOC from the association though they knew that the previous owner had some pending maintenance dues. The notice in this effect was prominently displayed on the entrance to the lift and passage. Also they have chosen not to become members and membership fee is still not paid. They forcefully park their vehicle in the parking area eligible for their flat, though the parking space is not yet allotted to them by the association for non- submission of NOC before moving in to the flat. They are very irregular in payment of monthly maintenance dues as well as other payments towards society developmental charges. The maintenance is due for more than 18 months. They do not stay in the apartment and they don’t visit as the flat is not occupied. The association has been following up for the dues since long time without a luck. Very recently, when they visited the flat for renting it out, association approached them to discuss about the pending dues. However, they argued and said they are not going to pay anything as the flat was not occupied. We referred them to the relevant clause of the association bye laws which talks about amount as decided by the association . Suddenly they became violent and came attacking one of the association members. Considering the verbal abuse (foul language) & loud threatening words and basis the CCTV footage we filed an NCR with the local police station. Though outside of the police station, they agreed to clear the dues but there is no action from their side yet. Hence the association has decided to proceed legally to collect the dues with interest, as per bye laws. In this reference, we approached a legal help but one of his advises have raised further questions. He says, we can’t proceed for collection of dues, unless the association is registered with some specific authority (just like municipality authority), even if we are registered with Registrar of Society and are fully compliant with regard to annual filing and Income tax filing as well. Is there any such law which stops the apartment association from collecting the genuine outstanding just for not registering with a specific authority? What is the legal remedy for recovery of outstanding dues from apartments owners and under what section laws? What is the procedure for initiating an action? Any valued opinion and guidance from the experts We would request expert opinion vis-à-vis laws in the state of Karnataka if any. Thanks in advance….