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