Now, if they were to be released for some reason - as in an order from a US federal district judge as an example - then Title 8 § 1182, would be germane. But, I believe even then, certain waivers can be granted by the executive branch. As an example, if someone would be a cooperating witness, they could theoretically be granted a visa, even if prior actions would preclude their admission.
Ya know, I see a lot of guys with them "terrorist hunting licenses" in their pickup's back window.