Is it ever ok for a dog to lie on a human?

It is not necessarily bad for a dog to be on top of a human if the HUMAN initiated it. For example, the human called the dog onto their lap. If it is the dog making the calls then it can be the dog being dominant. A dog that decides is a dog that is being the leader. Being on top is a dominant position in a dog's mind, but making the decisions is also a dominant position in a dog's mind. When humans are upset, dogs see this as a weakness. Keeping all of these facts in mind, you also need to know your dog and what frame of mind he is in, what frame of mind you are in and remain the leader at all times.