Claiming dependent

Just recently got divorced in June 2019. I have 2 kids with my ex. We have joint legal and physical custody of our kids.  The divorce decree says we each claim 1 kid on our taxes. My ex just recently got her taxes done and says she could claim both kids,because she has them 2/3 of the time and the new tax law ignores the divorce decree. I am saying I still am able to claim 1 child per the divorce decree. Who is correct?