s 20 Subsidiary legislation may be retrospective
Notwithstanding the absence of any express provision in any Act or other written law, where such Act or other written law empowers any person to make subsidiary legislation, such subsidiary legislation may be made to operate retrospectively to any date which is not earlier than the commencement of the Act or other written law under which it is made or, where different provisions of that law come into operation on different dates, the commencement of that law under which it is made: Provided that no person shall be made or shall become liable to any penalty in respect of any act done before the date on which the subsidiary legislation was published.