24 Judgment No. CCZ 2/18 Constitutional Application No. CCZ 86/15 factors relevant to the achievement of the legislative purpose. The different treatment must correspond to the nature of the difference. No legislation in any practical sense is possible without some kind of classification. The very nature and purpose of every legislation depend on the choice of some subject to the exclusion of the rest and some arena for its operation. This selective quality is inherent and implicit in every legislation. The constitutional guarantee of the right to equal protection of the law cannot be understood and construed in such a manner as to make legislation impossible for all practical purposes. To what class or classes of persons or things a statute should apply is, as a general rule, a legislative question. The Legislature is the best judge of the needs of the particular classes. Given that the criterion for the imposition of the financial obligation was termination of an employee’ contract on notice and that the object of the obligation retrospectively imposed was payment of compensation for loss of employment, there had to be a differentiation of treatment between employers and employees. The effect of the retrospective application of the statute had to be the classification of people in employment relationships into employers who terminated employees’ contracts on notice on or after 17 July 2015 and the employees whose contracts were terminated on notice. As long as the retrospective application of the change is rationally related to a legitimate legislative purpose, the constraints of equal protection of the law have been honoured even when the legislation imposes a new obligation based on past acts.