While I in no way condone this behavior, I think that "kidnap" is a bit strong when you consider that she is his mother. It's just a custody dispute. Good grief. Take a child away from his own mother because she loved him enough to break the law to keep him? Is that the only recourse our wrongheaded justice system has--take the child away and put him in a foster home?
The really sad irony is that if the is kid 17, he could have just waited until he was 18 to contact his dad. He would have been free to do as he pleased and and, as long as his dad was willing to be discreet, kept his mom out of trouble.
I mean, yes, she broke the law. Yes, it's serious. But the consequences are off the hook stupid, IMO.