I. Introduction
The doctrine of operative fact is a jurisprudential principle in Philippine constitutional law that recognizes the legal effects of a statute, executive act, or order prior to its declaration as unconstitutional or invalid by a competent court. It serves as an equitable tool to mitigate the harsh and disruptive consequences of a retroactive nullification, acknowledging that real-world transactions and legal relations have already been founded upon the assumption of the act’s validity. The doctrine tempers the general rule that an unconstitutional law is void ab initio (from the beginning).
II. The General Rule: Void Ab Initio
The foundational principle is that a law or act declared unconstitutional is deemed a legal nullity from its very inception. It confers no rights, imposes no duties, and affords no protection. In theory, all acts performed under it should be considered void. This is rooted in the supremacy of the Constitution.
III. The Exception: The Operative Fact Doctrine
The operative fact doctrine is an exception to the void ab initio rule. It recognizes that before the declaration of unconstitutionality, the statute or act was an operative factit existed in law and was acted upon by the government and the people in good faith. The doctrine validates the legal consequences that arose from such good-faith application during the period the law was considered valid. It prevents chaos and injustice that would result from unwinding all completed and closed transactions.
IV. Jurisprudential Foundation
The doctrine was crystallized in the landmark case of De Agbayani v. Philippine National Bank (G.R. No. L-23127, April 29, 1971). The Supreme Court, speaking through Justice Fernando, held that while a law declared unconstitutional is void, “the existence of a statute prior to such declaration is an operative fact and may have consequences which cannot justly be ignored.” The past cannot always be erased by a new judicial declaration.
V. Key Elements for Application
For the doctrine to apply, two key elements are generally present:

VI. Distinction from Prospective Overruling
It is crucial to distinguish the operative fact doctrine from prospective overruling.
Operative Fact Doctrine: Looks backward. It validates the legal effects of the void law during the period it was operative. The declaration of unconstitutionality still applies to the case at bar and retrospectively, but certain effects are recognized as facts.
Prospective Overruling: Looks forward. The court declares a new rule of law but applies it only to future cases, explicitly exempting the instant case and all past actions. The unconstitutional law is effectively applied to past events.
VII. Limitations and Non-Application
The doctrine is not absolute. It will not be applied:

VIII. Illustrative Cases
Application: In Planters Products, Inc. v. Fertiphil Corporation (G.R. No. 166006, March 14, 2008), the Court, while striking down a levy, did not order a refund of collections made prior to the declaration, applying the operative fact doctrine to the government’s good-faith implementation.
Non-Application: In Republic v. City of Davao (G.R. No. 191083, July 18, 2012), the Court refused to apply the doctrine to a tax exemption granted by a void ordinance, as the local government unit acted beyond its authority (ultra vires) from the start.
IX. Practical Remedies
For practitioners, the doctrine necessitates strategic consideration in litigation and transaction planning. When challenging a law’s constitutionality, counsel should specifically pray for the court to define the temporal scope of its ruling. A plea for prospective application or a clear invocation of the operative fact doctrine may be necessary to protect clients from disruptive retroactive effects. For transactions, while reliance on a statute is presumed valid, caution is required for laws that appear facially or substantively questionable. In the aftermath of a declaration of unconstitutionality, practitioners must analyze whether their client’s situation involves closed, good-faith transactions that may be insulated under the doctrine, or whether they are entitled to a retroactive remedy such as restitution. Distinguishing between executed acts (which may stand) and executory rights (which may be extinguished) is paramount. Furthermore, in claims for refund or restitution of payments made under a void law, the doctrine often serves as the government’s primary defense; overcoming it requires demonstrating the law’s patent invalidity or the government’s bad faith.