prisoner in my state because of joint custody

hello my name is "connie". i have lived in nevada for 27 years. when i divorced my third husband we were given joint custody of our son. now, because we have joint custody my divorce papers state that i have to obtain consent from my ex-husband to move my family out of the state of nevada. my question is, do i still have to obtain consent from my ex-husband if he no longer lives in nevada. if so, what if he denies to give me consent, what would my next step be.