behaviour modification

Question
What advice would you give to an owner who's dog sits on the sofa and growls when he is asked to get down?

Answer
That it's dangerous behavior, of course depending on the breed of dog, as I don't know if this is a 4 lb. Chihuahua or a 80 pound German Shepherd that's on the couch.  The dog doesn't respect the owner as a leader or as boss.  I would never take that from a dog.  Need to hire a trainer to fix the issue.