"This decision from Judge Leon will have broad ramifications for the tech, telecommunications and media sector for decades to come", said Daniel Ives, the chief strategy officer at GBH Insights.
The Justice Department has six days to ask the judge to stay his ruling, though Leon said he hoped the government would have the "good judgment, wisdom and the courage" not to do so.
President Donald Trump also once weighed in on the deal, commenting that an AT&T victory would put too much power "in the hands of too few" ― but many speculated that his aversion to the merger had more to do with his issues with CNN than anything else (Turner Broadcasting is CNN's parent company).
Leon said the evidence and testimony provided by the government were faulty and that it never proved the merged entity would have increased leverage over its competitors. Bush appointee, handed down his decision approving the $85 billion merger with no conditions on Tuesday afternoon, following months of oral arguments and deliberations. The "drop dead" deadline for the merger to be completed is June 21.
AT&T Inc, which owns DirecTV, awaits a court ruling on Tuesday that will determine if it can buy Time Warner Inc, a decision that could prompt a cascade of pay TV companies buying television and movie makers and the first big test of the Trump administration's antitrust teams.
Because of AT&T's ownership of DirecTV, it can drive a harder bargain with other distributors that want Time Warner content, the government's lawyers argued during the trial.
Waiting in the wings are potential big-billions deals involving 21st Century Fox and Disney, Verizon and CBS, T-Mobile and Sprint.
Bloomberg via Getty Images AT&T CEO and Chairman Randall Stephenson exits federal court in April.
The Justice Department had repeatedly suggested the judge consider forcing AT&T to divest some of Time Warner's cable channels.
Leon, in his remarks during the ruling, strongly urged the government not seek a stay that would hold up the close of the deal. The government's star witness was Carl Shapiro, an economist at the University of California, who used an economic model to predict that consumer cable bills could rise by $500 million annually in aggregate by 2021.
"We are pleased that, after conducting a full and fair trial on the merits, the Court has categorically rejected the government's lawsuit to block our merger with Time Warner", McAtee said in a statement.
AT&T has said it needs to buy Time Warner to compete with the likes of Amazon, Netflix and Google in the shape-shifting streaming-TV environment.