If I never provided the noncustodial parent w/ 8332 Release of Claim in previous years, can I both 1. claim my son this year and 2. revoke for future years as a notice?

Can I submit the 8332 form to REVOKE the noncustodial parent from claiming our dependent on their taxes if I NEVER submitted a 8332 form in previous years allowing him to do so? Basically, can I revoke something I've never previously signed before? Or can I just file my taxes first, since I am the custodial parent (per court documents & children spend most nights out of the year with me, beyond 50/50).