She can't take your son to an undisclosed location in another state w/o committing abduction. The usual procedure is to get an order permitting this from the family court first. If you were an abuser that would weigh heavily in the balance against you. If you want to do something about it you'll have to go back to the family court that allowed her to move away.
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California law strongly favors frequent and continuing contact between both parents and their children. A parent that interferes with the other parent's relationship with the children, risks losing custody or having custody granted to the other parent. Child abduction is taken seriously, and absent some immediate danger to the children, can bring serious consequences. You should consult with a local attorney as soon as possible and file an ex parte application to get the children back or at least obtain a visitation schedule. Feel free to give me a call for a free initial consultation. 415-835-6777.
Disclaimer: You should discuss your situation with a local attorney, as the above statement is a general overview and does not take into account all of the factual considerations in your case. Nothing in this statement creates an attorney-client relationship.