A person seeking to reenter to testify could apply for a nonimmigrant visa. By regulation, and in order to avoid criminal liability under INA 236, 8 U.S.C. 1326, they would need consent to reapply. A waiver of inadmissibility, under INA 212(d)(3)(A), would waive inadmissibility under INA 212(a)(9)(C). It might be faster to obtain parole into the United States to testify as a witness, but (a) it might be beneficial in other ways to have obtained consent to reapply, and (b) an individual can affirmatively schedule a nonimmigrant visa interview, which might be handy if a litigant wants to show that one party is taking unfair advantage of the unavailability of a witness. Thanks to Chuck Roth.

If the government refuses to agree to a humanitarian parole to allow a witness to enter the United States to testify, defense counsel in the criminal case could file a motion to dismiss for violation of Due Process, Equal Protection, and Compulsory Process.