A federal appeals court on Wednesday revived a constitutional challenge to a private-sector firm’s role in conducting unclaimed property audits on behalf of Delaware.

The narrow ruling by the U.S. Court of Appeals for the Third Circuit came on an appeal by Plains All American Pipeline, which had challenged a lower court’s earlier findings that broader claims against both the state and independent auditor Kelmar Associates were too speculative to support the lawsuit.

In a precedential opinion, a three-judge panel of the appeals court upheld the bulk of the dismissal, but allowed a procedural due process claim against Kelmar to continue, saying that the Boston-based firm’s own financial stake in the outcome of the audits had rendered the issue ripe for review.

“Given the nature of a biased adjudicator claim, adversity exists,” Senior Judge D. Michael Fisher of the U.S. Court of Appeals for the Third Circuit wrote for the court. “Because the conduct being challenged by Plains is the appointment of Kelmar to conduct this audit, the harm alleged for this claim is not based on a contingency; it is based on conduct that has already occurred.”

Fisher was joined by Judges Michael A. Chagares and Anthony J. Scirica.

Plains’ lawsuit was one of several high-profile cases to challenge Delaware’s system for collecting unclaimed property, which accounts for the state’s third-largest source of revenue. The practice has come under attack in Delaware, since a 2016 district court ruling in the case Temple-Inland v. Cook blasted Delaware’s escheat laws for allowing overly aggressive audits.

Delaware has since amended its statute to address constitutional concerns, and lawmakers have said that additional changes may be needed in the future.

In Plains’ case, the company refused to submit to a state audit initiated by Kelmar in 2014 and opted instead to bring its constitutional challenge in the U.S. District Court for the District of Delaware.

Among other things, Plains had contested Delaware’s threatened use of estimation to determine how much unclaimed property should be returned to the state. The Houston-based pipeline operator also argued that Delaware unfairly targeted wealthy companies in an improper attempt to boost its coffers.

In court filings, Plains said that Kelmar was paid for its work on a contingency basis and that both the firm and the state had a mutual interest in getting companies to pay up.

“Although Kelmar obediently does Delaware’s bidding, it is not acting solely in Delaware’s interest,” Plains said. “It is motivated by the contingency fees it reaps when audit targets pay unclaimed property assessments.”

U.S. District Judge Richard G. Andrews, however, tossed the facial challenges last August on the basis of standing and ripeness, saying that it was too early in the audit for Plains to have suffered a constitutional injury.

As for the law’s application to Kelmar, Andrews said that no controversy existed because the auditor had not yet sought a subpoena to enforce its authority to access to Plains’ records. On appeal, Plains argued that the harm occurred in Delaware’s appointment of a biased and self-interested third party to conduct the audit.

Fisher agreed, sending the question of the constitutionality of the relationship back to Andrews.

“Perhaps this arrangement is constitutional, as Delaware asserts, but that is a merits question,” he said.

Attorneys for the parties did not respond Wednesday to calls seeking comment on the ruling.

Plains was represented by Phillip B. Dye Jr., Deborah C. Milner, Jeremy C. Marwell and Christian Sheehan of Vinson & Elkins and James E. O’Neill III, Colin R. Robinson and Bradford J. Sandler of Pachulski Stang Ziehl & Jones.

Kelmar was represented by Stephen W. Kidder and Ryan P. McManus of Hemenway & Barnes and Marc J. Phillips of Manion Gaynor & Manning.

The case is captioned Plains All American Pipeline v. Cook.