Laws, as a general rule, should be prospective not retroactive. The rule is not absolute because it admits of some exceptions such as: 1.] When the law itself provides for its retroactivity (San Luis vs. San Luis, G.R. No. 133743, February 6, 2006); 2.] When the law is penal in nature and which is favorable to the accused who is not a habitual delinquent or recidivist; 3.] When the law is procedural in nature; 4.] When it creates new substantive rights; 5.] When the law is curative in nature (necessarily retroactive for the precise purpose to cure errors or irregularities). This kind of law to be valid must not impair vested rights nor affect final judgments (Frivaldo vs. Comelec and Lee G.R. 120295, June 28, 1996); 6.] When it is interpretative of other laws; and 7.] If the laws are of an emergency nature and are authorized by the police power of the government (Santos vs. Alvarez 44 O.G. 4259).
