Customs Tariff rules must be laid before Parliament for scrutiny and may be modified or annulled by both Houses. Section 10 requires that every rule made under the Act be laid before each House of Parliament for a total of thirty days (in one or more sessions). If, before the end of the session immediately following that period, both Houses agree to modify or annul the rule, the rule will thereafter operate only as modified or be of no effect; such modification or annulment does not affect the validity of anything previously done under the rule.