It's the law.
Ok, I know you are missing the point here. BUT HE SCREWED UP AND LOST CUSTODY! I say that the law, in that case, should not penalize the mom because dad is a deadbeat loser. That goes for either parent in this situation.
Then, after mom has struggled for years doing this on her own, whether she was good about it or not, he decides to show back up. Give me a break. He is a loser and when he lost custody, he should have no rights, ever again, period. This is one of those situations that should have permanent consequences.