Can Tenants Keep Couches On Their Balconies??

We have a tenant who has a black leather couch on their balcony.....isn't that considered an eyesore.. That tenant's children play in our parking lot(even in our catports) they ride their tricycles .we are fearful that one of these children will get hit by a car. It will be considered our fault... Some kind of law designating "play areas for children" rather than them playing in parking lots. We drive and park on?? ...