(Rodrigo Capote/Bloomberg News)

Opponents of the Federal Communications Commission’s decision to repeal net neutrality rules have outlined their chief arguments to a federal appeals court in Washington, in hopes of undoing the FCC’s move from last year.

The legal briefs reflect a widening front in the multipronged campaign by consumer groups and tech companies to rescue the ISP regulations, which originally barred providers from blocking websites or slowing them. With the FCC’s changes, Internet providers may legally manipulate Internet traffic as it travels over their infrastructure, as long as they disclose their practices to consumers.

The FCC’s decision to repeal the rules was “arbitrary and capricious,” said officials from the state of New York, the California Public Utilities Commission and others in court documents Monday — asking the U.S. Court of Appeals for the District of Columbia Circuit to overrule the agency.

The FCC was too credulous in accepting industry promises “to refrain from harmful practices,” the officials said, “notwithstanding substantial record evidence showing that [Internet] providers have abused and will abuse their gatekeeper roles in ways that harm consumers and threaten public safety.”

Another group representing Mozilla — the maker of the Firefox Web browser — as well as Etsy, Vimeo and a number of consumer organizations said the FCC’s core rule changes made no logical sense and improperly conflate high-speed Internet service with online applications.

In justifying the deregulation, the FCC had said broadband is more like an information service than a telecommunications service. The distinction is important, because the legal classification determines the extent to which the FCC may regulate the service providers. For example, the “telecommunications” classification had allowed the FCC, in 2015, to apply stricter rules to Internet providers that not only banned the blocking of websites but also imposed new obligations on carriers meant to safeguard customer privacy.

The FCC said in its rule change last year that while many Internet users now no longer rely on their Internet provider for crucial applications such as email or search, many Internet providers do still maintain these applications.

What’s more, the agency said, all ISPs perform tasks that fall under the definition of an information service, such as interpreting what a user means when they type “fcc.gov” into their browsers and translating it into an IP address that servers can understand. This system, known as the domain name system, is what allows people who are connected to the Internet to get from one site to another.

“While many popular uses of the Internet have shifted over time,” the FCC’s order said, “the record reveals that broadband Internet access service continues to offer information service capabilities that typical users both expect and rely upon.”

But tech companies and consumer groups told the court Monday that third-party services routinely carry out those same functions and that ISPs cannot lay claim to lighter regulation just because a portion of their business is involved in performing them.

“The FCC could not have reasonably concluded that a drop of DNS and caching in a sea of transmission transformed the service into something that could properly be called an information service,” the brief said.

The overall impression, the group said, is that of trying to deregulate all roads that lead to hotels by simply reclassifying the roads themselves as hotels.

“Never mind, continues the builder, that the road itself does not provide guests with any lodging, business conferencing, or beach recreation services,” the brief said. “That is the essence of what the FCC argues.”

Jonathan Spalter, chief executive of USTelecom, a broadband industry group, said Internet providers stand for clear, consistent rules that apply to websites and carriers alike.

“As this case winds its way through federal court, it is worth noting what has NOT happened since the FCC’s open internet order in May: the internet as we know it is still thriving, growing, open and continues to spin on its axis,” Spalter said in a statement. “The predictions made by some that ISPs would engage in throttling, blocking, and anti-competitive prioritization, have not happened.”

The FCC declined to comment. A representative for NCTA — the Internet & Television Association, another major broadband industry group, didn’t respond to a request for comment.

The court deadline for the FCC to file its response falls in October.