If the divorce decree (dated 2017) says non-custodial parent, who is also behind on child support payments, is allowed to claim child A, does he STILL need Form 8332?

I'm just confused.

The non-custodial parent is going to claim child A, as per the divorce decree, on his 2017 taxes. I'm seeing so many different answers when asking if I need to fill out Form 8332, because of our divorce decree. All I need is a simple yes or no. 

Do they count as the same thing now? Or not? Does he need Form 8332, or can he use the decree as proof of an agreement? Do I need to state that I have an agreement on my return, if I haven't filled out this form?