21.—(1) Proceedings may not be brought under regulation 20 alleging that a person has acted unlawfully by virtue of regulation 8 if the question of the lawfulness of the act could be raised (and has not been raised) in immigration proceedings (disregarding the possibility of proceedings brought out of time with permission).
(2) If in immigration proceedings a court or tribunal has found that an act was unlawful by virtue of regulation 8, a court hearing proceedings under regulation 20 shall accept that finding.
(3) In this regulation “immigration proceedings” means proceedings under or by virtue of—
(a)the Immigration Acts, or
(b)the Special Immigration Appeals Commission Act 1997.