I have some suggestions, but I'm sure that many would feel them to be restrictive...but then, what is a child's soul worth?
I would not spank...because with older children it's not easy to change a rebellious heart through spanking. I would remove all of their belongings except for their bed, and the basic clothes. No toys, games, fashion accessories, keepsakes, knick-knacks nothing. Just an empty room with a bed. I would restrict their activities to adult church, with me. No children's church, youth group, or children's Sunday school. I would make them a part of my life (which would be a selfless act on my part, since it would also restrict my activities. But most parents aren't that selfless.) I would always keep them with me and would work on enjoying life with them, listening to their thoughts, considering their opinions, and fellowship with them, and reestablishing the lines of communications. But I wouldn't allow myself to be manipulated by their attitudes. This would continue until there was long-term change of heart, and I saw it in their behavior and desires in life.
Of course, all of this will probably cause a major temper tantrum, threats to run away, and a miserable few weeks, but it won't get you thrown in jail, and eventually the child will realize and appreciate the selfless sacrifice the parents are making. In essence, the parents are telling the child we're doing this because I love you more than myself and I'm putting actions behind my words. I'm not just scape-goating my responsibility behind a spanking, but I'm willing to change our lifestyle because I care about you. It's important to remember that the children probably want a good relationship with their paretns, they just want it on their terms.