There are a handful of legal doctrines that can be difficult to comprehend, but the law of the case doctrine shouldn’t be one of them. Yet, time and again, the doctrine seems to perplex litigants, especially when deciding whether it is binding or discretionary, and whether it has any application to a trial court’s own prior rulings. The answers to both of these questions are important to understand before asking a court to revisit a prior ruling.

The basic rule is this: a ruling or holding stated in an appellate court opinion is binding on all inferior courts in all subsequent proceedings related to the same parties in the same action. (Morohoshi v. Pacific Home (2004) 34 Cal.4th 482, 491.)

The doctrine is invoked when a party takes an appeal, or writ petition, to an appellate court that decides the issues presented on the merits and remands the matter to the lower court for further proceedings. Consequently, the summary denial of a writ petition does not become law of the case on any of the substantive issues raised because it is not a decision on the merits. (Kowis v. Howard (1992) 3 Cal.4th 888, 894.)

The doctrine is strongest when flowing vertically, down to the inferior courts. A ruling or holding of the California Supreme Court is binding on the Court of Appeal, the Appellate Division of the Superior Court, and the Superior Court. A ruling or holding of the Court of Appeal is binding on the Appellate Division of the Superior Court, and the Superior Court. And a ruling or holding of the Appellate Division of the Superior Court is binding on the Superior Court.

But the law of the case doctrine can also have horizontal application. For example, an appellate court will generally follow the law of the case doctrine when asked to revisit an issue that it previously decided in an earlier appeal between the same parties in the same action. (Santa Clarita Organization for Planning the Environment v. County of Los Angeles (2007) 157 Cal.App.4th 149, 156.) “This is true even if the court that issued the opinion becomes convinced in a subsequent consideration that the former opinion is erroneous.” (Ibid.) However, appellate courts can exercise discretion not to apply the doctrine when necessary to avoid an injustice, or when there is an intervening change in applicable law made after the prior appeal. (Morohoshi, supra, 34 Cal.4th 482, 491-492.) What would rise to an “injustice” is open for interpretation but, presumably, it would involve some form of prejudicial error. In any event, because there is no horizontal stare decisis within the Court of Appeal, the doctrine would not apply in the rare event that the subsequent appeal returns to a different district or division, or a different panel of the same division. (See Cedar-Sinai Medical Center v. Superior Court (1998) 18 Cal.4th 1, 21.)

Interestingly, the California Supreme Court has recognized that the doctrine can have reverse vertical application. This happens when a District Court of Appeal renders a decision, the case is remanded to the trial court for further proceedings, and instead of prosecuting another appeal to the Court of Appeal, the Supreme Court grants a petition for review, i.e. the second appeal skips the Court of Appeal. (Searle v. Allstate Life Ins. Co. (1985) 38 Cal.3d 425, 434.) The Supreme Court would follow the earlier decision of the District Court of Appeal, despite the ordinary rule of “supremacy” that allows lower court decisions to be countermanded by a higher tribunal. (See Morrow v. Hood Communications, Inc. (1997) 59 Cal.App.4th 924, 930, (dis. opn. of Kline, P.J.) [describing supremacy rule].) At that point, the doctrine is applied purely for reasons of policy and convenience. (Searle, supra, 38 Cal.3d at p. 434.)

When it comes to a trial court’s own prior rulings (another example of “horizontal” application), the doctrine is discretionary. (See In re Marriage of Nicolas (2010) 186 Cal.App.4th 1566, 1577-1578.) The flexibility of a trial court’s interim rulings is essential to avoid having every interim ruling become a de facto final ruling.  (Ibid.)

Notwithstanding, a litigant may argue that the doctrine should apply when an action passes from one trial judge to another (think peremptory challenges to judges under Code of Civil Procedure section 170.6). As the Second District Court of Appeal put it: “For one superior court judge, no matter how well intended, even if correct as a matter of law, to nullify a duly made, erroneous ruling of another superior court judge places the second judge in the role of a one-judge appellate court.” (In re Alberto (2002) 102 Cal.App.4th 421, 427.) It would also lead directly to forum shopping, “since if one judge should deny relief, defendants would try another and another judge until finally they found one who would grant what they were seeking.”  (Ibid.) This principle, however, is nuanced.

Take K.G. Mullen, Inc. v. Team Transit Mix, Inc. (2014) 2014 WL 4967129. There, plaintiffs successfully obtained an order granting a default from a judge that included $529,326.27 in consequential damages. But, before any default judgment was signed—and for unexpressed reasons—the Superior Court reassigned the case to a different judge. The second judge issued an order requesting additional briefing on the damages sought and ultimately decided not to award any consequential damages—a half-a-million dollar haircut on plaintiffs’ default.

Plaintiffs appealed, relying on the Second District’s earlier case In re Alberto to argue that the second judge did not have the authority to revisit the first judge’s earlier ruling. Rejecting the argument, the appellate court made an important distinction: the danger of creating a “one-judge appellate court” is diminished when the transfer of the case to a different judge is “unilaterally effected by the court—not prompted by a litigant.” (K.G. Mullen, Inc., supra, at p. *2) This, the court said, meant that forum shopping was “of little concern” and, more importantly, the second judge’s ruling reflected “the solicitation and consideration of additional facts and argument—not merely a difference of opinion with the first judge.” (Ibid.) The law of the case doctrine had no application.

Reconciling In re Alberto with K.G. Mullen, Inc., it appears that discretionary application of the law of the case doctrine to a trial court’s prior rulings depends on whether the judge is revisiting her or his own prior ruling versus revisiting a ruling from a different judge. And, on that latter point, whether the case’s reassignment to the second judge was prompted by the litigant or prompted by the court itself. All this while keeping in mind that K.G. Mullen, Inc. is unpublished, meaning the original principle announced in In re Alberto should control the outcome.

In sum, the law of the case doctrine has binding application after an action between the same parties takes a detour to an appellate court that decides an issue, or issues, on the merits. Otherwise, courts are free to discretionarily apply the doctrine for the sake of policy and convenience. Having an understanding of the doctrine is key for deciding whether it’s worthwhile to revisit a court’s prior ruling, or whether to plow ahead with new and different arguments.

David is an Associate with Hanson Bridgett’s Appellate practice group where he focuses on writs, appeals, and law and motion. He has filed numerous amicus curiae briefs on an array of issues, and has been Counsel of Record for amici in both the California and United States Supreme Courts.