What can be done if a stepparent is attempting to assert rights to provide medical benefits?

My ex's husband is trying to assert himself by taking out medical polices on my children. He has done so without my consent and there was a court order that instructed my ex to have them removed. Her husband refuses to do so. There will be a hearing in two weeks for a determination of a Commissioners ruling, but I don't see how, as a third party, he can usurp my rights as my children biological father and custodial parent. They currently have medical, and in addition, if I sign for any services used under his health plan I'll wager I'd be liable for all expenses not covered under that plan. My ex is currently $12,000 in arrears, and hasn't worked in over 2 years. The current order clearly states that if she has the ability, and if it falls within a certain amount, that she is to provide insurance through her employer or union. Furthermore, under decision making she cannot make any non-emergency medical decisions. I'm thinking to contend that he has no rights or authority to do so, is not a party to the original action and has no standing before the court, and is setting something in motion that would create more liability for me than I've already absorbed due to her inaction if the court even entertains this idea.