Complex sentence: The Cinematograph Act, 1952 provides for certification of films by CBFC "having regard to the nature, content and theme of the film..." and doesn't have any provision for're-certification' of already-certified films.
Split into simpler sentences: The Cinematograph Act, 1952 provides for certification of films by CBFC "having regard to the nature, content and theme of the film...". As such, the extant law doesn't have any provision for're-certification' of already-certified films.