Got a thorny question of state law in your federal case? The federal court certainly has the power to decide it. Indeed, federal courts routinely decide questions of state law, doing their best to make an “Erie guess” as to the right result. But just because the federal court can decide the question doesn’t mean it will. There’s another option: certifying the question to the appropriate state supreme court.

Once rare and relatively unknown, the certification process has been gaining traction in recent years. In 2020, the U.S. Supreme Court issued two decisions (McKesson v. Doe, 141 S. Ct. 48, 49 (2020) (per curiam), and Carney v. Adams, 141 S. Ct. 493, 504 (2020) (Sotomayor, J. concurring)) discussing the importance of certification. And just two months ago, Justice Elena Kagan pondered during argument in U.S. v. Washington—a case involving a state law aimed at federal workers who got sick while cleaning up the Hanford nuclear site—whether certification to the Washington Supreme Court might be appropriate. Meanwhile, the U.S. Court of Appeals for the Ninth Circuit certified nearly four times as many questions between 2015 and 2019 (84) as it did between 1990 and 1994 (23).

Given the increased interest in certification, litigators of all stripes should understand the rules governing it. With that in mind, we briefly outline the basics, process and some relevant considerations below.


Certification allows a federal court to obtain a definitive answer from a state court as to a novel question of state law presented by a pending case. The federal court does not transfer the entire case to state court, nor does it cede its decision-making authority. Instead, the federal court simply asks the state court to opine on an unsettled legal issue and, once it receives an answer, applies that rule to the case at hand to reach a decision.

Questions appropriate for certification are both unsettled and potentially dispositive. But “certification is by no means ‘obligatory’ merely because state law is unsettled; the choice instead rests ‘in the sound discretion of the federal court.’” McKesson, 141 S. Ct. at 51. The Supreme Court has suggested that “sensitive” questions—such as those that “involve moral, social, and economic factors” or could impact the structure of state government—might be particularly appropriate for certification. Id. That’s because concerns about federalism and comity are at their zenith when a “dispute presents novel issues of state law peculiarly calling for the exercise of judgment by the state courts.” Id.; Carney v. Adams, 141 S. Ct. at 504 (Sotomayor, J. concurring).


To understand the process governing certification in a particular case, litigants must look to the relevant state law and court rules, as well as the local federal rules.

Certification is a creature of state law. The vast majority of states—49 of them, to be precise—as well as the District of Columbia, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands, have statutes or court rules authorizing their Supreme Courts to accept certified questions. North Carolina is the only state without a rule clearly authorizing certification. That said, acceptance of certified questions continues to be rare (or nonexistent) in some states that ostensibly permit it. For example, the Missouri Supreme Court has deemed responding to certified questions akin to issuing an unconstitutional advisory opinion and refuses to do so. On the other end of the spectrum is California, whose Supreme Court has been relatively willing to entertain such questions.

State law also determines which courts can invoke the process. The quintessential example of certification is when a federal Court of Appeals sends a question to a state supreme court. And indeed, all 49 states authorize acceptance of certified questions from at least one U.S. Court of Appeals. In addition, every jurisdiction but New Jersey specifically authorizes certified questions from the U.S. Supreme Court. Most jurisdictions also authorize certified questions from federal district courts—an option that should not be overlooked. And some jurisdictions go further, allowing certified questions from other state courts, bankruptcy courts and tribal courts.

Cases can be certified on a party’s motion or sua sponte. Most circuits, including the Ninth Circuit, lack specific rules on when or how to file a motion for certification. But a few circuits do have specific rules governing the process. For example, the Third and Seventh Circuits require any motion for certification to be included in the moving party’s brief. The Tenth Circuit rules, by contrast, provide that a “motion to certify should be filed at the same time as, but separately from, the moving party’s brief on the merits.”

If the state supreme court accepts the question, state rules take over once more. Those rules determine the extent of briefing and oral argument on the question and whether the state court can reformulate the question presented. Once the question has been decided, the state court will transmit the answer—sometimes a “yes” or “no,” but usually a more extensive explanation—back to the federal court.


If your case involves an unsettled issue of state law, you should carefully consider whether to ask for certification. In making your decision, you may want to take into account the composition of the relevant courts and their respective jurisprudential approaches. Some commentators have suggested that federal courts may feel more constrained by intermediate state court decisions, while the state supreme court is free to adopt whatever rule it deems correct. On a more practical level, if a question is certified, resolution of the appeal will almost certainly be delayed.

If you do decide to ask for certification, be prompt and mind the rules. Although not all circuits dictate the timing of such motions, earlier tends to be better, and waiting until after oral argument (or submission on the briefs) could be seen as gamesmanship. Also, if the relevant state law allows certification from district courts, consider asking for that—failure to do so may decrease the likelihood that an appellate court would grant a motion to certify. Finally, make sure you frame the questions carefully. One or two succinctly stated questions are more likely to be certified than a rambling list.

Even if neither side moves for certification, it could still happen. In fact, a recent study of the Third, Sixth, and Ninth Circuits found that the vast majority of certifications are made sua sponte. And of those cases, most certifications occurred after oral argument. Accordingly, if you think the possibility of certification might be percolating—even if no one has mentioned it—you should come to oral argument prepared to address the issue.

The key point is that certification should be on your radar, and you should consider it when formulating your litigation strategy. In other words, if you have a federal case involving a perplexing question of state law, don’t be taken by surprise if the court phones a friend.

On Appeals is a monthly column by the attorneys of the Complex Appellate Litigation Group LLP, an appellate boutique with offices in San Francisco, Los Angeles, and San Diego. Susan Yorke is of counsel with the firm. She previously served as a law clerk on the Ninth Circuit for two judges and as an Assistant Attorney General in the Appellate Division of the Oregon Department of Justice. Find out more about Susan and the Complex Appellate Litigation Group LLP at

This article originally appeared in The Recorder on September 21, 2022.