Structure n setback towards commercial activity

Dear Sir In the apartment building that we reside in, an area of 5.3 meter has been marked as the front set back area in the Guwahati Municipal Development Authority approved drawing. Now the tenants of apartment Block 1A who runs a Café (A Bistro House) wants to encompass the front set back area by putting up structure towards carrying out their commercial activity. To the best of our knowledge Set backs are common areas and are kept free where no construction either temporary or permanent can come up and if any such structure does come up is a violation of Municipal Development authority's norms. Setting up structure towards carrying out commercial activity is in our view a clear violation of the norms. Do the tenants have the right to use the Set back area towards their commercial activity. Ours is a co-Operative society and the original owners of the land had already been allocated individual apartment etc as per their terms with the builder. The tenant of Block 1A says that as per the rent agreement, the owners of unit 1A have allowed them the exclusive use of the land, however as per the agreement copy available with us the owners have already been given their due and every owner of the apartments have equal share on the portion of the land, setbacks included. Would be obliged for a clarification. Regards Sanjit Phookun Secretary Mandovi Apartments Primary Housing Co-Operative Society Ltd