WASHINGTON—A U.S. appeals court on Tuesday threw out federal rules requiring broadband providers to treat all Internet traffic equally, raising the prospect that bandwidth-hungry websites like Netflix Inc. might have to pay tolls to ensure quality service.

For consumers, the ruling could usher in an era of tiered Internet service, in which they get some content at full speed while other websites appear slower because their owners chose not to pay up.

"It takes the Internet into completely uncharted territory," said Tim Wu, a Columbia University law professor who coined the term net neutrality.

Adopted in 2010, the Federal Communications Commission rules said that companies like Verizon Communications Inc. and Comcast Corp. had to treat all similar content on their networks equally, whether it was a YouTube video or a home video posted on a personal website.