“(A) In general:

…the Attorney General may not remove an alien who is sentenced to imprisonment until the alien is released from imprisonment. Parole, supervised release, probation, or possibility of arrest or further imprisonment is not a reason to defer removal.

(B) Exception for removal of nonviolent offenders prior to completion of sentence of imprisonment:

The Attorney General is authorized to remove an alien in accordance with applicable procedures under this chapter before the alien has completed a sentence of imprisonment… [I]n the case of an alien in the custody of the Attorney General, if the Attorney General determines that the alien is confined pursuant to a final conviction for a nonviolent offense (other than an offense related to smuggling or harboring of aliens)… and the removal of the alien is appropriate and in the best interest of the United States; or in the case of an alien in the custody of a State (or a political subdivision of a State), if the chief State official exercising authority with respect to the incarceration of the alien determines that… the alien is confined pursuant to a final conviction for a nonviolent offense the removal is appropriate and in the best interest of the State, and submits a written request to the Attorney General that such alien be so removed.”

Nov. 30, 2017 - “U.S. Code – Title 8 – Chapter 12 – § 1231”