see - sc.judiciary.gov.ph/jurisprudence/2013/april2013/202242.pdf
"x x x.
It would not be amiss to point out, however, that as a general rule, an
unconstitutional act is not a law; it confers no rights; it imposes no duties; it affords no protection; it creates no office; it is inoperative as if it has not
been passed at all. This rule, however, is not absolute. Under the doctrine of operative facts, actions previous to the declaration of unconstitutionality are legally recognized. They are not nullified. This is essential in the interest of fair play. To reiterate the doctrine enunciated in Planters Products, Inc. v. Fertiphil Corporation: 32
The doctrine of operative fact, as an exception to the general rule, only applies as a matter of equity and fair play. It nullifies the effects of an unconstitutional law by recognizing that the existence of a statute prior to a determination of unconstitutionality is an operative fact and may have consequences which cannot always be ignored. The past cannot always be erased by a new judicial declaration. The doctrine is applicable when a declaration of unconstitutionality will impose an undue burden on those who have relied on the invalid law. Thus, it was applied to a criminal case
when a declaration of unconstitutionality would put the accused in
double jeopardy or would put in limbo the acts done by a municipality in reliance upon a law creating it.33
Under the circumstances, the Court finds the exception applicable in
this case and holds that notwithstanding its finding of unconstitutionality in the current composition of the JBC, all its prior official actions are
nonetheless valid.
x x x."
