That's a frightening story. It's great that authorities of both countries cooperated. One wonders how often this happens, and which border guard looked the other way or was bribed when they initially crossed. A friend and I took his son across the border to Canada for a few days, and the Canadian guards wouldn't let us out of the ferry compound without papers, a letter from his mom, and they also questioned the kid in front of us as "who is your dad, who is this guy, who is your mom, where is she right now... ." etc. Obviously he was older. They were divorced and she had primary custody, but the border guards didn't know that. They just saw a kid with two guys.
My Ex was in legal limbo for a few months back when S4 was S1. Her green card was expiring, and her citizenship process was going slowly. She was worried that she'd have to go back to Mexico. I told her that she would still stay with us, regardless of her status. She said that she was going to take our son back to Mexico if she was going to be deported because "children belong with their mothers." It frightened the heck out of me. I didn't respond, but was already thinking to call lawyers to get ahead of it... .
