Bought land under urban land celeing act?

my grandfather purchased 8 kottah in 1979 december in ranchi out of 57 kottah land of seller after taking permission from the government under urban land ceiling act 1976 and sale of deed registered in ranchi and name mutated. and built a bungalow on it ..we have the case no.. Now after 39 years when we try to sell it someone comes with a sale of deed of january 1979 of the whole 57 kottah registered in kolkata... they say we purchased 8 months before you entire 57 kottah but they dont have permission from government under ULCA... we ask were they sleeping from 39 years.. they are doing case on us and not letting us sell... they did not take permission is their registry valid?