In the state of Michigan can a physically and mentally abused 17 year old move out legally and freely ?

My boyfriend who is 30 days from being 17 years old has constantly been physically abused (choking, kicking, slapping, etc), verbally abused and etc. His parents have been abusing him for many years now and that he is almost seventeen he is sick of the way he is treated and plans on moving in with my family. Legally, they cannot take him off our property if he is seventeen. right? And if he chooses to stay or move in with us the parents technical cannot do anything. Several calls to the police have been made and reports of the abuse have been made also. The police have done nothing but send him home back with his abusive parents as though it is alright, but is that alright? My main question is, what could the parents do if he decided to move in with us and legally when he is seventeen is he allowed to? Without getting emancipation