(a) a by - law or determination is made for the purposes of a Customs Tariff proposed in the Parliament or of a Customs Tariff as proposed to be altered by a Customs Tariff alteration proposed in the Parliament; and
(b) the proposed Customs Tariff becomes a Customs Tariff or the proposed alteration is made, as the case may be;
the by - law or determination shall have effect for the purposes of that
Customs Tariff or of that Customs Tariff as so altered, as the case may be, as
if the by - law or determination had been made for those purposes and the
proposed Customs Tariff or the Customs Tariff as proposed to be altered, as
the case may be, had been in force on the day on which the by - law or the
determination was made.