MetroPCS Communications has become the second operator to sue the FCC over its net neutrality rules.

In an appeal filed with the U.S. Court of Appeals for the District of Columbia, MetroPCS argued that the FCC exceeded its authority in issuing its open Internet order, which passed by a 3-2 vote in December.

Verizon filed an appeal in the same court last week. It also alleges the FCC overstepped its authority in issuing the rules.

In a statement provided to Reuters, MetroPCS CEO Roger Linquist said the company filed the lawsuit to “ensure that the concerns of competitive wireless carriers, like MetroPCS, are addressed.”

The contentious regulations prohibit broadband Internet service providers from “unreasonable network discrimination” and require wireless operators to let subscribers access lawful content over their networks.

House Republicans have threatened to block the FCC’s new net neutrality regulations from going into effect and last week praised Verizon’s legal challenge.

“We welcome the decision by Verizon, and hopefully others, to demand their day in court to block the FCC’s misguided attempt to regulate the Internet,” said Congressman Fred Upton (R-Mich.), chairman of the House Energy and Commerce Committee, Greg Walden (R-Ore.) and Lee Terry (R-Neb.), chairman and vice chairman of the Subcommittee on Communications and Technology.