Time Warner shares traded more than 5 percent higher in aftermarket trading.
The widely anticipated ruling comes amid pent-up interest in forging combinations across the entertainment and communications industries. CNBC's parent company, Comcast, has been eyeing a $60 billion offer for the Twenty-First Century Fox studio and production assets that are currently part of a deal with Disney.
Comcast was reportedly waiting for a favorable ruling to unleash its offer for Fox. And many believe it would set off a flood of other dealmaking. Strategas said in a research note that companies brought $296 billion back to the U.S. from overseas operations in the first quarter after the tax cuts and "are flush with cash to do deals."
Fox rose more than 5 percent.
Shares of Comcast were lower in aftermarket trading, while Disney fell 1.5 percent.
The deals combine giants of communications distribution and transmission with behemoths in content production. In the AT&T deal, the phone and cable company is taking on Turner Broadcasting's movie and television production businesses and channels like CNN.