Retrospective validation protects past excise recovery actions, permitting recovery where prior judicial rulings had barred it. Retrospective validation legitimises excise recovery actions back to 17 November 1980, overriding prior judicial impediments and covering demands previously held time barred due to approved classification or price lists, provided notices were issued within the retrospective temporal scope; finalized matters require notices referencing the amendment and pending appeals should be met with affidavits drawing attention to the retrospective provision so adjudication proceeds under the amended law.