The law is very clear here. No matter what, it has been deemed that entering / exiting is a fundamental liberty to USC’s, not a privilege. CBP must establish a claim of citizenship and once established there is no law or penalty or action that can be applied that allows them to prevent you going on your way.
Now, what they do with you while they are establishing citizenship? Not really something I’d like to test out. Between when you enter and they follow up they can pretty much do what they want. Thats something to avoid.