1. The meaning of the word retrospective is backdated or to look back. Therefore, the retrospective law is a law that has backdated effect or is effective since before the time it is passed. The retrospective law is also referred to as ex post facto law.
2. Whether the Retrospective law is ultra vires to the Constitution or against the law of natural justice? The answer to this question depends upon the nature of the law passed. Whenever the retrospective law impairs the obligation of contract, it is void. However, law which only varies the remedies, divests no right, but is curative and merely cures a defect in the proceedings is fair and valid.
3. Article 20 of the Constitution of India prohibits the legislature to make retrospective criminal laws, however, it does not prohibit a civil liability retrospectively i.e. with effect from a past date. Therefore, tax can be levied retrospectively. However, in tax law, if there is a penal provision, retrospectivity is not permitted to that extent.
4. The validity and scope of retrospective legislation can be understood and analysed from some of the judgments, of the Hon’ble Apex Court and High Courts, wherein the guidelines and law has been laid down therein, as follows: