A bicameral group of Democrats urged a federal appeals court to uphold a lower-court ruling that blocked U.S. Immigrations and Customs Enforcement from using or viewing taxpayer addresses it obtained via its data-sharing agreement with the IRS. “The data sharing here was illegal and threatens federal revenue, adversely affecting all taxpayers,” the lawmakers wrote. “Those assurances drew millions of taxpayers into the federal tax system, generating billions of dollars in revenue,” the brief stated. AdvertisementThe IRS-ICE data-sharing agreement has been the subject of other lawsuits. A June watchdog report, meanwhile, found that ICE hadn’t met data safeguarding standards before the agency inked the April 2025 memorandum of understanding with the IRS.