Help.. What would Buddha say to do in this custody situation?

I have been trying to get myself into a non reactionary state and all my instincts seem to tell me to do the opposite of what Buddha would have taught. My ex is withholding visitation from me but we have a joint custody agreement in place. He won't answer my texts, won't let my daughter call, has pulled her out of school and keeps her locked up in the house like a prisoner. I am very concerned about her well being, she has been depressed at his house and had been requesting to move back in with me before all of this started. I could go to court and file an enforcement motion along with relief in the form of legal fees, and jail time for him. While this feels reactionary is it? Would I be doing harm if I stand up for my daughter? I don't want a fight and I don't want to see anyone hurt further.