As per case facts, the appellants filed writ petitions challenging the retrospective application of an Explanation to Section 5 (1-A) of the Karnataka Sales Tax Act, 1957, which clarified the ... definition of taxable turnover to exclude the tax component. This Explanation was inserted in 1996 but made effective from 1988. Their challenge was unsuccessful in the High Court, leading to these appeals. The question arose whether this retrospective operation, especially when dealers argued they could not pass on the tax burden to consumers for the past years due to prior legal interpretations, was unreasonable and arbitrary, making the legislation unconstitutional. Finally, the Supreme Court held that the legislature has the power to impose tax retrospectively, provided it is not arbitrary or unreasonable. The Court noted that the period during which the appellants could not have passed on the tax burden was limited. It concluded that such an effect was not sufficiently unreasonable or harsh as to invalidate the Explanation and dismissed the appeals, though allowing for payment in instalments.