My son (16, US citizen) has moved to his father overseas. I want to claim him but does Form 8332 apply when father is not US citizen and can't file US tax return anyway?

Child is US citizen, I am too, father is not and doesn't live in the US and is not a greencard holder. Father is therefore by law not required to file a US tax return. Do I still need to have him sign a form 8332 or a piece of paper saying he's not claiming my son on a US tax return?