Erecting metal sheds in setbacks

Hi - Mine is a building with 20 flats and I am one of the owner. Of this 20, about 14 owners are a group and they have hiked the maintenance and have been collecting the maintenance. The others have no choice but to pay. Corpus amount is also collected per flat and it is not deposited in a bank but the amount is already utilised for CCTV, erecting metal sheds in the setback area (2 sides) and other works. Nothing or very little is left in the corpus fund. Now, they have erected a metal shed in the setback area on the third side and removed the little garden present on the two sides of th building. Before the works are taken up, I have expressed my disagreement with the proposed works but they have gone ahead and completed it without my consent. My questions - 1. Can I get the metal sheds erected in the setback areas removed through municipal agency? as the setback areas must be open to sky all the time for safety, security and ventilation. Also, is not it illegal to cover up the setback areas in a building premise? Thanks.