28 CFR § 2.32 - Parole to local or immigration detainers.
(a) When a State or local detainer is outstanding against a prisoner whom the Commission wishes to parole, the Commission may order either of the following:
(1) Parole to the actual physical custody of the detaining authorities only. In this event, release is not to be effected except to the detainer. When such a detainer is withdrawn, the prisoner is not to be released unless and until the Commission makes a new order of parole.
(2) Parole to the actual physical custody of the detaining authorities or an approved plan. In this event, release is to be effected to the community if detaining officials withdraw the detainer or make no effort to assume custody of the prisoner, providing there is an acceptable plan for community supervision.
(b) When the Commission wishes to parole a prisoner subject to a detainer filed by Federal immigration officials, the Commission shall order the following: Parole to the actual physical custody of the immigration authorities or an approved plan. In this event, release is to be effected regardless of whether immigration officials take the prisoner into custody, providing there is an acceptable plan for community supervision.
(c) As used in this section “parole to a detainer” means release to the “physical custody” of the authorities who have lodged the detainer. Temporary detention in a jail in the county where the institution of confinement is located does not constitute release on parole to such detainer. If the authorities who lodged the detainer do not take the prisoner into custody for any reason, he shall be returned to the institution to await further order of the Commission.