GR: 15 days after completion of publication in OG or newspaper of general circulation
Exception: The law can provide its own date of effectivity, i.e., it can provide for a period less than or greater than 15 days after publication before the law takes effect.
• Publication is MANDATORY even if the law provides its own date of effectivity.
• Internal regulations of admin agencies binding only the agency need not be published.
COMPLIANCE WITH THE LAW:
Ignorance of the law excuses no one from compliance therewith.
(Ignorantia juris neminem excusat)
Generally, rules are not retroactive.
1. When the law itself expressly provides
Exception to the exception: ex facto law when retroactivity impairs the obligation of contract
2. Remedial statutes
3. Curative statutes
4. Laws interpreting other laws
5. Laws creating new rights
6. Penal laws when favorable to the accused who is not a habitual delinquent
ACTS VIOLATING MANDATORY OR PROHIBITORY LAWS ARE VOID
Exception: When law itself authorizes their validity