This was taken from SCOTUSblog:
In a 7-2 decision, the Court ruled that local governments have no constitutional duty to protect from private violence an individual who is shielded by a court’s restraining order. Such individuals do not gain an enforceable interest in that protection, the Court declared in an opinion by Justice Scalia. The case was Town of Castle Rock v. Gonzales (04-278).
So basically, don’t expect the cops to help you out when your estranged husband kidnaps your children and ultimately kills them. That restraining order doesn’t mean a thing to them.