ON PETITION FOR REHEARING
STEWART, Justice:The defendants, James C. and Brett Lewis, petitioned for a rehearing, contending that our holding in the main opinion that the Utah Guest Statute is unconstitutional should be applied prospectively only. In particular, they argue that the ruling *676should not apply to them because the plaintiffs cause of action arose before Critch-ley v. Vance, Utah, 575 P.2d 187 (1978), was decided, which sustained the constitutionality of the Guest Statute.
The general rule from time immemorial is that the ruling of a court is deemed to state the true nature of the law both retrospectively and prospectively. In civil cases, at least, constitutional law neither requires nor prohibits retroactive operation of an overruling decision, Loyal Order of Moose v. County Board of Equalization, Utah, 657 P.2d 257, 264-65 (1982); Vaughn v. Murray, 214 Kan. 456, 521 P.2d 262, 269 (1974), but in the vast majority of cases a decision is effective both prospectively and retrospectively, even an overruling decision. Loyal Order of Moose, 657 P.2d at 264; State Farm Mutual Insurance Co. v. Farmers Insurance Exchange, 27 Utah 2d 166, 168, 493 P.2d 1002, 1003 (1972). Whether the general rule should be departed from depends on whether a substantial injustice would otherwise occur. Cf. Great Northern Railway Co. v. Sunburst Oil & Refining Co., 287 U.S. 358, 53 S.Ct. 145, 77 L.Ed. 360 (1932).1
We may, in our discretion, prohibit retroactive operation where the “overruled law has been justifiably relied upon or where retroactive operation creates a burden.” Loyal Order of Moose, 657 P.2d at 265. For example, we have limited or prohibited retroactive application of decisions invalidating or reinterpreting certain statutes. See Timpanogos Planning and Water Management v. Central Utah Water Conservancy District, Utah, 690 P.2d 562 (1984); Rio Algom Corp. v. San Juan County, Utah, 681 P.2d 184, 195-96 (1984); Loyal Order of Moose, 657 P.2d 257. In these cases, the challenged statute had been justifiably relied on, and complete retroactive application of the statute would have irreparably burdened the individuals or entities who relied on it. See also Board of Education v. Salt Lake County, Utah, 659 P.2d 1030 (1983).
The defendants in this case do not argue that they justifiably relied on our prior decisions sustaining the constitutionality of the Guest Statute. There is no evidence that the defendants knew of the Guest Statute and relied upon it in offering a ride to the plaintiff. The bare assertion by defendants that our decision overrules pri- or cases sustaining the constitutionality of the Guest Statute, is insufficient to prohibit its retroactive application.2
The defendants contend that the Guest Statute had been held constitutional when the accident in the present case occurred and when it was filed, and only thereafter was held unconstitutional. They argue that our main opinion holds that the Utah Guest Statute was constitutional in 1978 when Critchley v. Vance, Utah, 575 P.2d 187 (1978), was decided, but has since become unconstitutional because of the enactment of the Motor Vehicle Safety Act, No Fault Insurance Act, and other provisions discussed in Part II, supra. That is not the case.
In the first place, the main opinion did not hold that the Guest Statute was constitutional when Critchley v. Vance, Utah, 575 P.2d 187 (1978), Thomas v. Union Pacific Railroad Co., Utah, 548 P.2d 621 (1976), or Cannon v. Oviatt, Utah, 520 P.2d 883 (1974), was decided. It is true that many of the statutory provisions relied on in the Court’s main opinion to demonstrate a changed legislative approach to the problem of highway carnage were in force when those cases were decided. But our ruling that a statute which is constitutional when enacted may, because of changed *677conditions, become unconstitutional was not based solely on the enactment of those statutes. Our ruling was also founded on the changing use of the automobile in light of current conditions and clear-cut illogical discriminations that make the statute blatantly unfair. Furthermore, as we pointed out in footnote 12 of the main opinion, supra, neither Critchley nor Thomas independently analyzed the Guest Statute, but simply relied on Cannon v. Oviatt, Utah, 520 P.2d 883 (1974). And Cannon's equal protection analysis did not address the equal protection arguments discussed in Part II of the Court’s opinion.
The equal protection analysis that was made in Cannon is not an adequate reason to prohibit retroactive application of the present decision. On the contrary, since plaintiffs constitutional rights are at stake, the case for retroactive application is even stronger. Indeed, the injustice that would result if those guests who have been injured after Critchley were barred from a remedy far outweighs any prejudice to the defendant in the case.
The petition for rehearing is denied.
HALL, C.J., and HOWE and DURHAM, JJ., concur.
ZIMMERMAN, J., does not participate herein.. In criminal cases, the prospective or retroactive effect of decisions involves a different range of considerations. See Rio Algom Corp. v. San Juan County, Utah, 681 P.2d 184, 195 (1984).
. We are well aware that the real party in interest is really an insurance company. On rehearing, the insurance company could have moved for leave to file an amicus brief had it felt aggrieved by a retrospective application of the decision. No insurance company, or any other party, moved to file an amicus brief. Our own research strongly suggests that the decision will have very little, if any, adverse impact on the public liability insurance industry.