One of the country’s richest men is claiming Colorado owes him money—from three years ago, thanks to a COVID stimulus bill. Phil Anschutz, who Forbes ranked No. 50 on its rich list with $10.5 billion net worth, and his wife Nancy have sued the Colorado Department of Revenue, claiming changes made to the federal tax law allow them to claim a refund on their 2018 tax return. The couple pointed to the CARES Act, passed by Congress last year in response to the COVID pandemic, which retroactively suspended limits on “excess business losses” between 2018 and 2020. The two claim the changes apply to how state laws are calculated. Colorado attorneys claim the law is only applied for future tax years, citing departmental rules adopted in June 202o.

The Anschutzes haven’t publicly disclosed how much money they’re trying to claw back, and the case was sealed from public view last month. The state attorney general filed a motion for the case to be dismissed but that’s redacted as well, and it only reveals general specifics of how the two sets of tax rules clash. Anschutz owns stakes in several fields, including Los Angeles’ Staples Center, film company Walden Media, and a hand in creating the U.S.’s Major League Soccer.