OTARD is the relevant law about sat dishes but you may not like it. OTARD says you have the right to use an antenna or sat dish but it limits this to area's that are your exclusive access like a balcony or fenced yard. It does not guarantee you the right to mount it on the roof or to drill holes etc. If you don't have LoS from an exclusive access area or don't have any exclusive access area you are SOL as far as OTARD goes.
Now there might be more general laws that would grandfather you in and prevent them from making you remove the sat dish or at the very least let you get out of your lease with out paying penalties because they are changing the terms of the lease.
Edit added links
http://www.fcc.gov/guides/over-air-reception-devices-rule
http://www.dbstalk.com/showthread.php?t=192544
Now there might be more general laws that would grandfather you in and prevent them from making you remove the sat dish or at the very least let you get out of your lease with out paying penalties because they are changing the terms of the lease.
Edit added links
http://www.fcc.gov/guides/over-air-reception-devices-rule
http://www.dbstalk.com/showthread.php?t=192544