Ex wife wont bring kids home?

My husbands ex wife refuses to bring his kids home. He has residential custody and she gets them everyother weekend, 2 weeks in the summer when agreed upon by both of them and any other time disscussed between them. this was her weekend. She was to bring them home yesterday at 5pm. She didn't. We had big plans for the holiday. She said she wasn't bringing them back. We called the sheriffs dept where she lives. They went and talked to her but said there's nothing they can do. How is this right? My husband has not talked to her at all. She will not answer his calls or texts. We had no clue what was going on except for what his adult daughter was telling us she said. How can a divorce decree clearly state these things and she doesn't have to follow it? It caused a big mess with the family and that's all she wanted. We still do not know when the kids are coming home. She's never done this before but she's never actually brought them home on time at 5pm. Its always 6 or 7 or 8 or whenever she feels like it. This also causes a problem with the girls ( 12 and 10). I know they love their mother but she is ruining them. We have them in counseling bc of their horrible behaviors and they even told the counslers there's no rules at their moms and its all fun and she just buys them whatever they want and let's them do whatever they want. All this does is cause problems when they come home and they do have rules and don't get every article of clothing or toy that they want. She also gets them no other time even when the kids beg her. only when its convienent for her. What can we do to stop all of this besides taking her to court and spending thousands of dollars? And how can the police allow her to get away with it?