law: 21. Revocation of postponement certificate.-
  (1) If, at any time, while a postponement certificate is in force, it appears to the Central Government that, by reason of any change in the circumstances of the qualified person to whom the certificate was granted or of his employer, where such certificate was granted on the application of such employer, the certificate ought to be revoked or the period for which it was granted or last renewed ought to be shortened, the Central Government may apply to the National Service (Hardship) Committee, and that Committee may either reject the application or cancel the certificate or vary it by shortening the period.
  (2) Where an application is made under sub-section (1), the person to whom the postponement certificate in question was granted, and where such certificate was granted on the application of an employer, such employer, shall be entitled to be heard on the application and the provisions as to appeals contained in section 20 shall apply in relation to the application as if it were an application for the grant of a postponement certificate.