I'm pretty sure she would had have to notify your husband BEFORE moving, and then he could had taken up an attorney to try and stop her from moving.
I have sole custody of my son, yet I still have to tell my ex well in advance if I plan to move, in case he opposes it.
He should get a lawyer (yeah, I know, they are expensive), and try and get a set visitation schedule, or even the return of the child. Here, moving without informing the other party, to try and stop access for the non-custodial parent, is sometimes grounds to a change of custody! I wouldn't dare do that...!!!