My ex and i have joint custody of our boys in ny ..he wants to move to cali? what should i do?

My boys reside with him for the past 6 yrs i see them every weekend...he is a jehovahs witness and my entire divorce is done so that i don't interfere with his religion he didn't want to pay me alimony and child support so he had everything done up and pretty much told me if i didn't sign it he would take them away from me..they go to there church 3 or more times per week or i would see them more and the younger ones get home from school late...i work overnites so it's hard for me and at the moment i don't have my own car...about a month ago he told me had full cutody and was moving to cali ..i asked him for a copy of the divorce papers cuz i knew i would have never agrred to that...i was right we have joint...what should i do my kids want to stay with me and im unsure of the laws in Ny...please help!!!