retrospective legislation

Laws which take away or impair vested rights acquired under existing laws, or create a new obligation, impose a new duty, or attach a new disability in respect of transactions or considerations already passed. 16 Am J2d Const L § 413. A statute which changes or impairs a present right by going behind it to give to anterior circumstances an efficacy which they did not have when the right accrued, or which relates back to and gives to a previous transaction a legal effect different from that which it had under the law when it was completed. International Mortgage Trust Co. v Henry, 139 Kan 154, 30 P2d 311; Clark Implement Co. v Wadden, 34 SD 550, 149 NW 424. A statute is not rendered retroactive merely because the facts or requisites upon which its subsequent action depends, or some of them, are drawn from a time antecedent to the enactment. See Reynolds v United States, 292 US 443, 78 L Ed 1353, 54 S Ct 801. A statute which does not change the legal effect of prior facts or transactions is not unconstitutionally retrospective merely because it relates thereto, or because it relies thereon to aid in fixing the present status of a person, or because some requisites for its action are drawn from a time antecedent to its passage. State ex rel. Sweezer v Green, 300 Mo 1249, 232 SW2d 897, 24 ALR2d 340.