(Bloomberg) -- Investment firms shouldn’t be allowed to keep half a billion dollars Citigroup Inc. accidentally sent them because the payment wasn’t due for three more years, legal experts said in asking a court to overturn the ruling.A group of law professors said in a brief filed Thursday with the federal appeals court in Manhattan that the lower-court ruling, allowing Revlon Inc. lenders to hold on to $504 million the bank wired them last August, misapplied legal precedent and could harm the industry’s standards.“The sheer magnitude of the transfer, constituting nearly 100 times the size of defendants’ scheduled coupon payments, was a giant ‘red flag,’” the professors told the court. They said the prepayment of the 2016 loan, at par and without notice, “constituted another glaring red flag that would have caused a reasonable person to inquire.”The law shouldn’t encourage similar, “serving, self-imposed ignorance in situations where it is nearly costless for a party” to “uncover and remedy the error,” the group said in its brief. The group isn’t a party to the case, but the court can consider its views.$900 Million BlunderThe conflict started after Citigroup inadvertently wired more than $900 million to asset managers for the Revlon lenders and then asked for it back. The bank sued firms, including Brigade Capital Management, HPS Investment Partners and Symphony Asset Management, that wouldn’t return the funds. It unexpectedly lost that battle in February.The embarrassing blunder forced Citigroup to answer to regulators and tighten its internal controls. The ruling was a boon to creditors, which had been locked in a battle with billionaire investor Ronald Perelman’s struggling cosmetics company over previous restructuring maneuvers.Read More: Citi Asks Court to Reverse $500 Million Transfer DecisionCitigroup has asked the appeals court to overturn U.S. District Judge Jesse Furman’s decision, saying it “sent shockwaves through the markets and generated outcry across the financial industry.” Oral argument in the appeal will be held in August or September.In its brief to the court, the group said the funds “were not due until the term loan matured in 2023,” and full repayment required prior written notice from both Revlon and Citibank that never occurred and was never questioned. The payment occurred outside of the contract between the investors, the company and the bank, which was acting as administrative agent on the loan. That should have “put a reasonable lender on notice of Citibank’s mistake,” the group said.‘Manual Touches’The Loan Syndications and Trading Association offered similar arguments in its own brief, saying the mistaken payment has already “significantly disrupted” the drafting and negotiation of credit facilities and the expectations of participants in the market. Mistakes will happen because the often automated transactions require “manual touches,” the trade group said.Furman’s decision letting the investment firms keep the money was based on a 1991 New York state court case, Banque Worms v. BankAmerica International. In that case, New York’s highest court ruled that under a principle called discharge for value, when a third party mistakenly sends money from a debtor to a creditor, the creditor can keep the payment if it didn’t realize it was sent in error and didn’t make any misrepresentations. But the mistaken payment in the Banque Worms case was money due to the creditors at the time it was sent, the group said.Read More: Citi Faces ‘Finders Keepers’ in Fighting $500 Million RulingThe ruling could have “substantial, detrimental effects” on the industry, including adding costs and risks in the leveraged loan market, “discouraging parties from engaging in collaborative contracting and punishing those who do,” and introducing “uncertainty into both new and already existing leveraged loan agreements,” the group said.The group includes Columbia Law School professors Eric Talley, Talia Gillis and Ronald Gilson, University of California at Berkeley professor Robert Bartlett, University of Michigan professor Albert Choi and University of Pennsylvania professor David Hoffman, as well as Edward Morrison, co-director of the Richard Paul Richman Center for Business, Law, and Public Policy at Columbia.The appeal is Citibank NA v. Brigade Capital Management LP, 21-487, U.S. Court of Appeals, Second Circuit (Manhattan). The lower-court case is Citibank NA v. Brigade Capital Management, 20-cv-6539, U.S. District Court, Southern District of New York (Manhattan).For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2021 Bloomberg L.P.