Housing society charged penalty for keeping plants in window

I own a flat in Chennai, Tamilnadu. Recently the housing society charged a penalty of Rs.500 for keeping potted plants in 1.5 feet window sill area outside of my bedroom window. They took away the potted plants and kept in their custody. The manager sighted a society bylaw claiming window sill as a common area where the owner cannot keep anything. I disputed the bylaw as nowhere it was mentioned window sill/ledge as a common area and requested to remove the penalty charged over email. I gave reference links of few cases where a housing society cannot charge penalty for things like keeping potted plants in window sill. The manager ignored it and refused to reverse the penalty. later i kept two pots on the edge of window, again they were taken away and another Rs.500 penalty has been charged to me. Its been two months and both penalties are appearing in my commonfloor group app account which is used by society to issue maintenance invoices and drawing interest. What is the law says and what are the next steps i should take as a flat owner?