The process, known as “throttling”, could still land AT&T in hot water, however through a fine by US regulator the Federal Communications Commission.
The US Court of Appeals for the Ninth Circuit ordered a lower court to dismiss the throttling lawsuit, which was filed by the Federal Trade Commission in 2014.
The FTC accused AT&T of failing to inform consumers that it would throttle the speeds of heavy data users on unlimited plans. The suit claimed some customers experienced speeds 90% slower than less frequent users.
According to Reuters, a spokesperson for AT&T said the US operator was “pleased with the decision.”
An FTC spokesman said the agency has not yet decided whether to appeal. "We are disappointed with the ruling and are considering our options for moving forward," an FTC spokesperson wrote to the news agency in an emailed comment.
The FCC could still hit AT&T with a fine worth $100 million. It proposed the figure in June last year, although AT&T said at the time it would contest the fine.
