Prospectivity of Laws
In general laws should be prospective not retroactive. However, there are some exceptions:
1. If the laws themselves povide for their retoractivity (Art. 4 Civil Code).
2. If the laws are remedial in nature.
3. If the statute is penal in nature, provided:
a. It is favorable to the accused or convict.
b. The accused or convict is not a habitual delinquent as defined in Art. 22 of the Revised Penal Code.
4. 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)
5. If the law is curative (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)