8 Judgment No. CCZ 2/18 Constitutional Application No. CCZ 86/15 The grounds on which the applicants challenged the constitutionality of the transitional provision were summarised by Mr Mpofu in argument as follows – (1) Law cannot retrospectively impose financial obligations; (2) Law cannot alter existing positive legislation retrospectively; (3) The legislation has the effect of forcing the applicants to pay workers without the benefit of labour; and (4) Retrospective application of s 12C(2) to the applicants through the transitional provision produced inequality in the treatment of the parties to the contract of employment. The contentions on which the applicants’ case is based are central to the debate concerning the extent to which the Constitution provides substantive protection against retrospective legislation. PRINCIPLE OF RETROSPECTIVITY Retrospectivity involves the application of new rules to transactions that have already been consummated. A retrospective statute is one which gives to pre-enactment conduct a different legal effect from that which it would have had without the passage of the statute. The most obvious kind of retrospective statute is one which reaches back to attach new legal rights and duties to already completed transactions.