What do I do if local law enforcement will not help me stop a stalker?

What do I do if the county I reside in keeps dropping the ball? My sister has had many issues with the father of her children. He will not let her and her children be, he refuses to sign custody papers and generally terrorizes them. She has had to turn to staying with family, hiding her vehicle and is now afraid to walk out her door alone. She has had 2 Orders of Protection issued, the first was not served until 2 days before it's expiration and the second she let expire on the advice of her lawyer because in a criminal trespass case he was ordered a year no contact with her. He has been showing up at her house and over the weekend when we called the police we were informed that the no contact order that was handed down at his August 24, court date was never served to the county jail and there for they could not act on it. The officer that told us that also told us that we should call them if we saw him driving by as we are all aware that he is driving on a revoked license and no insurance. This afternoon our mother called the police station and informed him that she knew for a fact that he would be driving and where and what time (we are very desperate to get him where he can not hurt my sister or her children). This officer basically informed her that even if he pulled him over he would not arrest him but just issue a ticket that our family was trying to "black ball" this man. We are all at our wits end the county/city keeps dropping the ball and the following, stalking, and threats continue to get worse. The issue is this is not his first go around with our county. His last relationship ended this same way. He tried to run my sister off the road while her children were in the car she drove straight to the police station and the cop let him go with a warning. From there he followed her and she had to dial 911 again he was let off with a warning. Then he vandalized her car on private property this is where the criminal trespass charges came from. While awaiting his court date she had to call the authorities again for following her and trying to cause her to have an accident with the kids in the car. He was pulled over and let go (even though he had no license or insurance). The County just keeps letting him get away with this and we are afraid for her and her children's safety. What do we do?