29 CFR § 525.17 - Revocation of certificates.
(a) A special minimum wage certificate may be revoked for cause at any time. A certificate may be revoked:
(1) As of the date of issuance, if it is found that misrepresentations or false statements have been made in obtaining the certificate or in permitting a worker with a disability to be employed thereunder;
(2) As of the date of violation, if it is found that any of the provisions of FLSA or of the terms of the certificate have been violated; or
(3) As of the date of notice of revocation, if it is found that the certificate is no longer necessary in order to prevent curtailment of opportunities for employment, or that the requirements of these regulations other than those referred to in paragraph (a)(2) of this section have not been complied with.
(b) Except in cases of willfulness or those in which the public interest requires otherwise, before any certificate shall be revoked, facts or conduct which may warrant such action shall be called to the attention of the employer in writing and such employer shall be afforded an opportunity to demonstrate or achieve compliance with all legal requirements.