Gabby, our situation is "joint shared custody" it's the most perfect 50/50 in our state. We alternate "from week to week" and since we've been swapping Mondays after school for her to take them from my custody without my permission on a Sunday evening was violating the court order. That was the conclusion of the responding police that evening. The court order states no specific time of day custody is transferred but since she removed them one day early against my wishes and instruction she is in violation. If a specific time of day had been documented they said they could have charged her with a crime and removed the children from her and returned them to me.
I can only assume from your comment you have a higher (even if only slightly) degree of custody of your children than your X. If the situation you describe existed everywhere then X's could remove children everytime they attended a birthday party, field trip, sleepover or attended school without the custodial parent's presence.
"Fear is the mind-killer" Muad'Dib Me 53, XW 44, DD 14, DS 12 Bomb and OM 12/15/06 Separated 01/02/07 Divorced 05/13/08 X married OM(OMH) 08/2009 Married 06/09/13