What justifications did Lomov give to Natalya and Chubukov to prove that he is the rightful owner of Meadows ?

Lomov said that his aunt’s grandmother gave the free use of these Meadows in perpetuity to the peasants of  Chubukov's grandfather, in return for which they were to make bricks for her. The peasants belonging to Chubukov’s grandfather had the free use of the Meadows for forty years, and had got into the habit of regarding them as their own, when in fact they belonged to Lomov's family.