The Texas attorney general continues the state’s legal challenge against the Environmental Protection Agency.

Texas Attorney General Greg Abbott has filed a brief on behalf of nine states, challenging the EPA’s Timing and Tailoring Rules, which they say improperly attempts to regulate greenhouse gas emissions under the federal Clean Air Act.

The EPA’s Timing Rule claims that the agency must regulate greenhouse gas emissions from stationary sources once it also regulates them from mobile sources, such as motor vehicles. The Tailoring Rule ignores greenhouse gas permitting thresholds originally established by the Clean Air Act, and replaces it with criteria of the EPA’s own making, according to the brief.

Abbott argues that the Clean Air Act was not designed to regulate greenhouse gas emissions, since they say that the emissions are not directly harmful to people.

Under the Clean Air Act, a stationary source such as a factory or foundry that has the capacity to emit more than 250 tons of a regulated substance must undergo arduous federal permitting requirements. The EPA’s Tailoring Rule lays out different guidelines, changing the permitting requirements to 75,000 tons per year.

The states argue that the Administration is moving forward with regulations that are unlawful under the Clean Air Act, despite the EPA’s acknowledgement that the rules would produce “absurd results” and regulatory “gridlock.”

Texas is currently challenging all six of the EPA’s greenhouse gas regulations in federal court.