Even though AT&T has already closed its acquisition of Time Warner, the deal may not be out of the woods just yet. CNN reports that the U.S. Justice Department filed notice Thursday that it is appealing the court decision approving the merger.

“Judge Richard Leon, who presided over the lawsuit the DOJ had brought to block the deal, ruled last month that the government had failed to show that the deal violates antitrust law, and in his opinion ripped apart its case,” CNN reports.

The corporate machinations have been proceeding as though the deal is done — including the renaming of Time Warner as WarnerMedia, which CNN notes has been set up as a separate unit from the rest of the company, in part because of the possibility of an appeal.

“The Justice Department sued to stop the deal last year, saying that a distributor, AT&T, owning the likes of HBO, CNN and Warner Bros. would harm consumers by causing an increase in prices and would hurt innovation and competition,” CNN reports. “But after a six-week trial, Leon said he didn’t buy that, and signed off on the deal with no conditions and knocked down the government’s contentions point by point.”

The report also notes: “The ruling was seen as a green light for other companies to pursue mergers, and in the ensuing months, bidding wars have erupted between Comcast and Disney for big chunk of 21st Century Fox’s assets.”