Can the police become involved in a child visitation matter?

Was it legal for police officers to accompany your sons' father to your house?  Yes, often law enforcement will "keep the peace" between parents.  Did they tell you that they were there to make sure you let your son go with his father?  That may not have been proper as there is no order to enforce.  There is a fine line between keeping the peace and enforcing orders.  Police officers can not enforce visitation unless there is a court order.  If you feel that they acted improperly you can complain to their superior, however, I would suggest that you do so in writing, carefully explaining what happened, and explaining that your son's father knows people in the department who are now stepping over the line as a favor to him.  If they were out of line and doing him a favor then there could be serious consequences for those officers.