2 C.F.R. § 180.315
May I use the services of an excluded person as a principal under a covered transaction?
(a) As a participant, you may continue to use the services of an excluded person as a principal under a covered transaction if you were using that person's services in the transaction before the person was excluded. However, you are not required to continue using that person's services as a principal. You should decide whether to discontinue that person's services only after a thorough review to ensure that the action is proper and appropriate.
(b) You may not begin to use the services of an excluded person as a principal under a covered transaction unless the Federal agency responsible for the transaction grants an exception under § 180.135.