Net neutrality advocates are heading to court Friday for what may be their best chance to restore federal regulations banning broadband providers from blocking, throttling, or otherwise discriminating against lawful content.

The Federal Communications Commission passed robust net neutrality protections in 2015. But in December 2017, the now Republican-controlled FCC voted to jettison those rules after a contentious public comment period during which bots flooded the agency's website with fake comments.

Advocacy groups, internet industry organizations, and state attorneys general quickly filed suit against the FCC, arguing that its decision to overturn the Obama-era protections was unlawful. Those suits were consolidated into a single case, which will be heard Friday by three judges on the US Circuit Court of Appeals for the District of Columbia.

The suit raises two main questions: whether the FCC broke the law by failing to consider evidence that went against its allegedly foregone conclusion that it should overturn the Obama-era rules, and whether it was legal for the FCC to stop considering broadband internet a telecommunications service, like telephone calls, and instead consider it an "information service" like Google or Facebook.

In its own brief, the FCC called the lawsuit "meritless."

Net neutrality advocates want the court to restore the old rules, Markham Cho Erickson, an attorney representing the non-government organizations in the suit against the FCC, said in a press conference Wednesday. But exactly what would happen if the FCC loses will largely be up to the court. A decision could take months, and there's a good chance that the losing side will appeal.

The decision will also affect states, such as California and Washington, that passed their own net neutrality rules after the FCC repealed its rules. Shortly after California's governor at the time, Jerry Brown, signed a sweeping net neutrality bill into law in September, then-attorney general Jeff Sessions filed suit against the state. The state and the US Department of Justice later agreed to delay the case until after the lawsuit over the FCC rules is decided.

The lawsuit is not the only effort to restore net neutrality. Last year the Senate passed legislation that would have restored the rules, but the House never voted on it. Given the long odds that Congress will pass, and President Trump will sign, a bill to restore net neutrality, the case represents the best shot advocates have for restoring those protections nationwide.

Arbitrary and Capricious?

One key issue in the case is whether the FCC violated the Administrative Procedure Act, which forbids federal agencies from making "arbitrary and capricious" decisions. The brief from the organizations challenging the FCC alleges that the agency's about-face on net neutrality, less than three years after approving those rules, was arbitrary and capricious, and ignored evidence that contradicted its preferred decision. For example, the agency refused a request from the National Hispanic Media Coalition, one of the groups bringing the suit, to include informal complaints filed with the FCC related to net neutrality in the record during the public comment process.

LEARN MORE The WIRED Guide to Net Neutrality

In its brief, the FCC argued that it had reasonably denied the coalition’s request, saying it was “exceedingly unlikely” that the informal complaints would raise issues not included elsewhere in the proceeding.

Much of the case the FCC made for repealing the rules revolved around the idea that the Obama-era net neutrality rules harmed investment broadband infrastructure, despite evidence, as WIRED has reported, that this wasn't the case.

The Brand X Case

The FCC considered broadband internet providers to be telecommunications providers until 2002, when it reclassified cable internet services as information services. The decision was challenged by an internet service provider called Brand X. The Supreme Court ruled in the FCC's favor in 2005.