A federal appeals court on Tuesday ruled in favor of the Federal Communications Commission and upheld its repeal of Obama-era net neutrality protections, issuing a mixed decision that also appeared to open the door for state and local governments to try to introduce their own rules.

In a nearly 200-page decision, judges on the D.C. Circuit Court of Appeals largely sided with the FCC and its Republican chairman, Ajit Pai, over their decision two years ago to unwind Internet rules that required AT&T, Comcast, Verizon and other service providers to treat all Web traffic equally. The judges found “unconvincing” the arguments of a collection of tech companies, consumer advocates and government officials that had challenged the repeal.

But even as the court upheld the legality of much of the FCC’s efforts, it offered a lifeline to net neutrality supporters by ruling that the FCC had overstepped its authority when it barred states from adopting open-Internet protections of their own. That is likely to embolden some states and local governments to pursue their own regulations. California, a trendsetter in Internet policy, adopted its own rules last year, though they were quickly challenged by the Justice Department and have not yet been enforced.

In doing so, the ruling threatened to spell even more legal wrangling at the FCC, which must reconsider elements of its net neutrality repeal, and in the court system, where the federal agency may still retain the ability to challenge states that adopt open-Internet rules, officials there signaled Tuesday.

The thicket of thorny issues could persist well past the 2020 presidential election, raising the potential that political changes in Washington could contribute new twists in telecom’s most intractable debate. FCC commissioners are appointed by the president.

In a statement, Pai on Tuesday heralded the decision. “The court affirmed the FCC’s decision to repeal 1930s utility-style regulation of the Internet imposed by the prior administration,” he said.

But net neutrality advocates indicated their fight isn’t finished. “When the FCC rolled back net neutrality, it was on the wrong side of the American people, the wrong side of history,” said FCC Commissioner Jessica Rosenworcel, a Democrat who voted against the repeal. “Today we learned in critical respects it was also on the wrong side of the law.”

Post tech reporter Hayley Tsukayama explains the idea of net neutrality and why its future could affect every Internet user. (Davin Coburn/The Washington Post)

“What this means is that net neutrality is still going to be a big part of our discussion in this country,” she continued. “There is still a fight to be had, and now it is both at the FCC and at the state and local level.”

“Our fight to preserve net neutrality as a fundamental digital right is far from over,” said Amy Keating, the chief legal officer at Mozilla, one of the companies that challenged the FCC repeal. She added Mozilla is “considering our next steps in the litigation.”

Pai, who was appointed to his position by President Trump, secured a repeal of the government’s net neutrality rules in 2017 with the support of the commission’s two other Republicans on a 3-to-2 party-line vote. Until then, federal open-Internet protections had prohibited providers such as AT&T and Verizon from blocking or slowing down access to Web content, or charging services such as Netflix and Hulu for faster delivery of their shows.

Pai justified the repeal by arguing that the rules, adopted under President Barack Obama, crimped telecom investment, stalling broadband build-out nationwide. In its place, the FCC required only that broadband providers be transparent about their practices. It shifted enforcement to the government’s competition watchdog, the Federal Trade Commission.

The repeal triggered widespread backlash: More than 20 state attorneys general banded with other city and state leaders as well as Internet companies such as Mozilla, the maker of the Firefox Web browser, in challenging the FCC’s efforts in court. Larger tech giants including Facebook and Google also filed supportive briefs through their Washington lobbying group, the Internet Association.

State regulators said the FCC had acted in an “arbitrary and capricious” manner, ignoring “substantial record evidence showing that [Internet service] providers have abused and will abuse their gatekeeper roles in ways that harm consumers and threaten public safety.”

Tech giants, meanwhile, contended that the FCC had embarked on an “abrupt about-face” in response to the election, choosing to subject AT&T, Verizon and their peers to less regulation based on a fundamental misunderstanding of how the Web works.

The battle played out over four hours of oral arguments in February, during which the D.C. circuit’s three judges at times seemed skeptical of the FCC. At least two of them harbored specific concerns about the effects of the agency’s repeal on public safety agencies. First responders from cities such as Santa Clara, Calif., had told the court they feared Internet providers could charge them more for faster delivery of critical communications during an emergency, adding that the FCC never took their arguments to heart.

Those concerns were reflected in Tuesday’s ruling, which ordered the FCC on Tuesday to return to the drawing board and reconsider the effects of its repeal on police officers, firefighters and other emergency services. The judges said that the agency hadn’t factored first responders and others, including low-income Americans, into its decision-making process.

“We look forward to addressing on remand the narrow issues that the court identified,” Pai said.

CORRECTION: An earlier version of this story attributed the rollback of the net neutrality rules to the Trump administration. The FCC is an independent agency whose commissioners are appointed by the president.

Rachel Siegel contributed to this story.