My ex husband is going to fill a cease and desist order against me?

My ex husband moved out of the country with our 3 children without telling me or anyone. We have been divorced for 2 years I had custody of our children for the first year until my life took a down fall. My husband was awarded primary physical custody and legal custody of our children. I was allowed to see my babies every week because my ex husband let me. My husbands sister told me he moved to The Czech Republic. I called him he just said to leave them alone and I won’t be seeing the kids ever again. If I try to contact them he will fill a cease and desist order against me. I don’t know what to do? I’m getting help for my addictions I’m taking parenting cles. I really don’t know how I can live without my children. Can he just up and leave? I need advice please.