Judge lets the Justice Department join the NAACP’s Clean Air Act suit over xAI’s Southaven turbines but refuses its request to dismiss the case

A federal judge in Mississippi has allowed the U.S. Justice Department to join the NAACP’s Clean Air Act lawsuit against X.AI Corp. and its subsidiary MZX Tech LLC over gas turbines in Southaven, but denied the government’s request to dismiss the case. U.S. District Judge Debra M. Brown of the Northern District of Mississippi signed the order Monday, Oct. 19, in NAACP v. X.AI Corp., No. 3:26-cv-74.¹

Brown wrote that the act gives the administrator of the Environmental Protection Agency an unconditional right to intervene in citizen suits, so the United States may take part on the administrator’s behalf, but that nothing in the statute or in Rule 41 of the federal civil rules lets it “unilaterally dismiss” another plaintiff’s suit. She ordered the government, if it wants to stay in the case, to file a pleading stating its claim or defense by Oct. 23; any response is due Oct. 30.¹

What the order decided

• The government’s Sept. 18 notice of appeal to the 5th U.S. Circuit Court of Appeals was premature, Brown wrote, because her statement at an Aug. 24 telephone status conference that she intended to deny the motion was not an order. The same day, a 5th Circuit panel of Judges Carl E. Stewart, Priscilla Richman and Catharina Haynes denied “only currently and temporarily” the government’s Oct. 9 request to pause the case pending appeal, because the district court had not fully decided the issue. The request may be refiled if the government is not allowed to take part in a preliminary injunction proceeding.¹²
• The court said the government’s national security concerns were not relevant to its power to dismiss.¹

Brown said the EPA and states are meant to be the law’s primary enforcers, but that this “does not mean that the federal government retains complete control over all Clean Air Act litigation.” The act bars a citizen suit only when the EPA or a state is “diligently prosecuting” its own case, she wrote, which the government did not claim.¹

The case

The NAACP and its Mississippi State Conference sued on April 14, 2026, alleging the companies built and ran a turbine power plant in Southaven without required permits. They seek an injunction and civil penalties of up to $124,426 per day per violation, the order says.¹ Mississippi Today reported that 69 trailer-mounted turbines power the company’s Southaven data center and that the state Department of Environmental Quality maintains the temporary units comply with state rules.³

The sides

The Justice Department’s June 15 filing said the NAACP “threatens American national, economic, and energy security” by seeking to cut power to AI work supporting military operations, and that the Clean Air Act, consistent with Article II of the Constitution, gives the federal government primacy over when and how the law is enforced.⁴

The NAACP called that position “unprecedented” in its July 10 opposition and said the government’s “claimed veto power finds no support in the Clean Air Act.”⁵ Patrick Anderson, a Southern Environmental Law Center attorney for the NAACP, told Mississippi Today, “We are pleased the Court saw through the Department of Justice’s deeply flawed arguments.”³

In a June 15 motion to dismiss, xAI and MZX argued they relied on the state agency’s finding that the portable turbines are “mobile sources” exempt from stationary-source permits, that the NAACP cannot sue on behalf of its members, and that the citizen suit provision violates Article II.⁶ In September, they backed the government’s stay request.⁷

What the records do not show

• The court will rule separately on xAI’s motion to dismiss, the order says.¹
• The order does not decide whether the turbines needed permits or rule on the NAACP’s June 12 preliminary injunction request to halt the plant.¹
• Mississippi Today’s Oct. 21 report carried no comment from the Justice Department or the company.³
• Records reviewed do not show whether the government filed its Oct. 23 pleading or will pursue its appeal.¹