An appeals court upheld federal government auctions of about $33 billion of wireless spectrum, saying it would be "imprudent and unfair" to undo them even though some rules governing them were invalid.

Tuesday's ruling by the U.S. Third Circuit Court of Appeals in Philadelphia allows Verizon Wireless, AT&T Inc, Deutsche Telekom AG's T-Mobile unit and others to keep billions of dollars of licenses they had won in the auctions, which took place between 2006 and 2008.

The auction process had been challenged by Council Tree Communications Inc, Bethel Native Corp and the Minority Media and Telecommunications Council, which contended that Federal Communications Commission rules for the auctions were unfair to smaller service providers.