The federal appeals court in Washington on Tuesday struck down important segments of the Federal Communications Commission’s open Internet order, which had kept service providers from blocking or slowing down users’ Internet connections to certain websites or applications.

The decision by the U.S. Court of Appeals for the District of Columbia Circuit is a strike against “Net neutrality,” the concept that service providers must treat all parts of the Internet equally and not favor any particular apps or websites by allowing them to load faster.

The court ruled that the FCC did not have the power to enforce its Net neutrality rules on Internet service providers because the commission had previously chosen not to classify those companies as broadband providers, which fall under the jurisdiction of the agency.

Proponents of Net neutrality said they were disappointed with the decision and fear what it may mean for the Internet.

“Its ruling means that Internet users will be pitted against the biggest phone and cable companies – and in the absence of any oversight, these companies can now block and discriminate against their customers’ communications at will,” Craig Aaron, president and chief executive of the watchdog group Free Press, said in a statement.

FCC Chairman Tom Wheeler said the agency may challenge the decision.

“We will consider all available options, including those for appeal, to ensure that these networks on which the Internet depends continue to provide a free and open platform for innovation and expression, and operate in the interest of all Americans,” Wheeler said in a statement.

But not all believe that the ruling foreshadows dark days ahead for the Internet.

“The elimination of these rules will better protect the ‘innovation at the edge’ of our networks, while further promoting investment and network operators’ flexibility to experiment and improve upon their architectures,” said Robert Atkinson, president of the Information Technology and Innovation Foundation, a nonpartisan Washington think tank.