What could the consequences be if your ex took your two children to Mexico without a notarized authorization letter from you?

If you joint custody he can take them on vacation but he does have to inform you. If he did not then you need to contact the police and an attorney so he is forced to bring them back. If you can contact him on your own first without getting the law involved then do that and give him a chance to return them voluntarily. If he chooses not to then he will be arrested and extradited then put in jail here and then get prosecuted by the law. The children will be taken from him and returned with probably official agents, unless you can go and get them yourself....Call an attorney to see what the best way to handle it for the kids is..less stress the bette * I wouldn't dispute any of the above. But if your question is really more like he took them for a day trip to Tijuana or vacation to Cancun or such, (no intent of not timely returning within visitation rights), but you believe he needed a notarized letter from you to do so: There is no legal requirement for a notarized letter for the travel that I know of. Under the new rules (like a week ago), even for a visit to Mexico everyone needs their passport though. (Used to be just about any document showing residency worked). * The consequences, if any, would be determined by the terms that were set out in the custody order and nothing else. If the mother holds primary custody, the non custodial father must receive written permission from her to take the minor children outside of the US.