Retrospective: looking backward; retroactive: acting backward. Affecting what is past; operating upon a past event or transaction. Retrospective is the more common. Every statute which takes away or impairs vested rights acquired under existing laws, or creates a new obligation, imposes a new duty, or attaches a new disability, in respect to transactions or considerations already past, must be deemed "retrospective." 2 That there exists a general power in the State governments to enact retrospective or retroactive laws, does not admit of question. The only limitation is the provision that the same shall not be such as are technically "ex post facto," or as "impair the obligation of contracts." A legislative body may by statute declare the construction of previous statutes so as to bind the courts in reference to all transactions occurring after the passage of the law, and, in many cases, thus furnish the rule to govern the courts in transactions which are past, provided that no constitutional right of a party concerned is violated. Congress cannot, under cover of giving a construction to an existing or expired statute, invade private rights, with which it could not interfere by a new or affirmative statute. But where it can exercise a power by passing a new statute, which may be retroactive in its effect, the form of words used cannot be material, if the purpose is clear, and that purpose is within its power. The settled doctrine of the Supreme Court is that "words in a statute ought not to have a retrospective operation unless they are so clear, strong and imperative that no other meaning can be annexed to them, or unless the intention of the legislature cannot be otherwise satisfied." United States v. Beyer, 31 F. R. 37 (1887). Society for Propagating the Gospel v. Wheeler, 2 Gall. 139 (1814), Story, J. See also Dash v. Van Kleeck, 7 Johns. *503-8 (1811), Kent, C. J. Story's definition quoted, Sturges v. Carter, 114 U. S. 519 (1885), Woods, J.; Rairden v. Holden, 15 Ohio St. 210 (1864), Brinker hoff, C. J. 3 Constitution, Art. I, sec. 10. Baltimore, &c. R. Co. v. Nesbit, 10 How. 401-2 (1850), cases, Daniel, J. • Stockdale v. The Insurance Companies, 20 Wall. 331-32 (1873), Miller, J.; Koshkonong v. Burton, 104 U. S. 679 (1881); Kring v. Missouri, 107 U. S. 221 (1882); [3 Bl. Com. 296; 1 Ala. 47; 31 id. 113; 17 Ga. 251; 68 22 Wall. 76; 95 U. S. 654-55; 17 Ct. Cl. 171; 2 Story, Ind. 310; 8 Pa. 163; 79 Va. 338. 4 Bl. Com. 185. * People v. Iams, 57 Cal. 120 (1880), Morrison, C. J. • Carter v. State, 82 Ala. 15 (1886), cases. Const. § 1393. Chew Heong v. United States, 112 U. S. 559 (1884), cases, Harlan, J., quoting United States v. Heth, 3 Cranch, 413 (1806), Paterson, J. (57)