Res judicata?

tenant got benefit once for depositing arrear of rent under specific rent legislation. later landlord files eviction challenging rent legislation jurisdiction admitting previous decree to be null and void and claims mesne profits, in WS tenant agrees to take previous decree to be void but says rent act applies and stops paying rent. now if court uphelds rent act jurisdicton then will the default in rent payment will be ground for eviction because benefit can be availed only once.