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No you are not permitted to stop paying support for any reason without a court order. As far as having her arrested, only if you go to court and request a judge start the process of having her charged with parental kidnapping. If this was a simple vacation out of the country it is unlikely they will charge her with kidnapping but could charge her with contempt.
In the end it is up to the judge to decide if this would be kidnapping or contempt. As for stopping the order you will want to petition the courts for termination based on her taking off with the kids. If the judge agrees he can suspend or temporally terminate the order until she returns.
She is definitely in contempt of court.....kidnapping is a possibility. What you may want to consider is filing a petition in court to demand that she return the children to the states immediately as this is interfering in your parental rights.
You can also request full custody based on her actions as well. Just because she has left the country doesn't mean she can get away with it.