BNP Paribas is asking a federal appeals court to overturn a landmark jury verdict that found the French bank liable for enabling human rights abuses in Sudan, arguing the trial judge misapplied both Swiss and U.S. law, Reuters reported Thursday.

The bank filed a 67-page opening brief with the U.S. Court of Appeals for the Second Circuit, challenging a $20.75 million verdict returned last year by a Manhattan federal jury in a class action brought by approximately 23,000 Sudanese refugees in the United States, according to Reuters. The jury award covers only three test plaintiffs, leaving significantly larger potential liability unresolved pending the appeal’s outcome, the outlet reported.

The class action, filed in 2016, alleged that BNP knew or should have known that by providing financial services to Sudan’s government between 1997 and 2011, it helped support a campaign of murder, rape, and torture against civilians, Reuters reported. The U.S. government recognized the Sudanese conflict as a genocide in 2004.

A central feature of the case is its application of Swiss law, a choice made by the original presiding judge, Alison Nathan, who reasoned that BNP conducted its Sudan-related banking primarily through a Geneva branch, according to Reuters. Nathan has since been elevated to the Second Circuit.

BNP’s appellate lawyers, from Gibson, Dunn & Crutcher and Cleary Gottlieb, argued that trial judge Alvin Hellerstein disregarded Switzerland’s own interpretation of its laws on critical issues. The bank pointed to a letter submitted shortly before trial by the Swiss ambassador to the United States, Ralf Heckner, who wrote that Hellerstein’s rulings did not reflect Swiss jurisprudence and amounted to what he called “a new U.S. court-created law,” according to Reuters. The ambassador, whose government has no monetary stake in the outcome, characterized the rulings as a challenge to Swiss sovereignty, the outlet reported.

BNP argued that under Swiss law, Sudan’s sovereign immunity from private suit is fatal to the plaintiffs’ case because Sudan, as the alleged primary wrongdoer, cannot itself be held liable, its alleged accomplice cannot be either, according to the report.

Plaintiffs’ lawyers disputed that position, describing the ambassador’s letter as citing virtually no legal authority and arguing that its arguments had already been raised and rejected, the news agency said. Plaintiff co-counsel Kathryn Lee Boyd told the outlet that applying foreign law is routine for U.S. courts and “not an affront to sovereignty,” while co-lead counsel Michael Hausfeld said BNP was recycling “a fanciful interpretation of governing law, claiming that international corporations can operate without regard to the human rights consequences of their actions.”

BNP also challenged Hellerstein’s evidentiary rulings, arguing he improperly allowed plaintiffs to reference the bank’s 2014 guilty plea to U.S. criminal charges for sanctions violations, which resulted in a penalty of nearly $9 billion, while barring the defense from telling jurors that BNP’s financial transactions with Sudan complied with more limited sanctions imposed by the European Union, the United Nations and Switzerland, Reuters said. The bank argued the imbalance prevented it from contesting whether it had consciously assisted wrongful acts.

The bank’s awareness of conditions in Sudan was not in dispute at trial. Hellerstein directly asked BNP Chief Operating Officer Philippe Maillard whether he knew the Sudanese government was guilty of human rights violations while the bank was conducting its financing. Maillard answered, “yes, your Honor,” Reuters reported.