Too bad for them.
They have zero, zilch, nada to say in the matter.
All the more reason, also, to begin deporting them now, no matter how long it takes. They can deport themselves at any time, but since there's no statute of limitations, they will be deported, sooner or later.
If the have minor American "citizens", they can choose to put them up for adoption, or take them on the return trip. When the kids reach adulthood, they can apply for return with conditions.