Oral arguments were presented Friday in the most prominent lawsuit challenging the federal government’s repeal of broadband access rules known as net neutrality.

The Federal Communications Commission approved the rules in 2015 to ensure internet users equal and open access to all websites and services. The commission, under new leadership, rolled the rules back in 2017.

The plaintiffs in the suit, led by the internet company Mozilla and supported by 22 state attorneys general, say the commission lacked a sound legal reason for scrapping the regulations. The government was expected to argue that the rules were repealed because of the burden they imposed on broadband providers like Verizon and Comcast.

The case, before the United States Court of Appeals for the District of Columbia Circuit, could wind through the courts for years. If the commission loses, it might try to rewrite its order rolling back the rules to avoid further legal challenges.