A new ruling in the xAI lawsuit literally tells us nothing

Okay – here’s a major update on the xAI gas turbine fight.

The xAI files

Every essay in this series is pinned to a question on the board at rachelandthecity.com/the-xai-files.

Remember when Mississippi told xAI its Southaven turbines didn’t need an air permit? A federal judge just read Mississippi’s own rules and said they weren’t exempt.

On October 30th, U.S. District Judge Debra M. Brown refused to throw out the NAACP’s lawsuit over the gas turbines at xAI’s site in Southaven.

The NAACP sued xAI and MZX Tech, the company behind the Southaven site, under the Clean Air Act. That’s the federal law on air pollution, and the whole case turns on one question. Is a turbine on a trailer a “mobile source”?

If it is, it doesn’t need an air permit in Mississippi. If it isn’t, it’s a stationary source – something that sits in one spot and pollutes, like a factory – and you need a permit before you build it.

The Mississippi Department of Environmental Quality – MDEQ – is the state agency that decides who needs an air permit.

On July 29th, 2025, MDEQ wrote to xAI’s Brent Mayo and said the turbines were exempt. Its reasons came down to two words. They were “mobile,” because each one would stay “affixed to a portable unit (i.e., a flatbed trailer).” And they were “temporary,” because as MDEQ understood it, each one would stay on site “for less than twelve (12) months.”

I wrote about that letter on September 15th. The rule MDEQ pointed to says “Mobile sources” and nothing else – no definition and no time limit.

So the judge went looking for a definition.

As she reads them, Mississippi’s air rules – the plan the U.S. Environmental Protection Agency, or EPA, approved for the state – borrow the federal government’s definition of a mobile source. Under that definition, she wrote, these turbines don’t move themselves, they aren’t meant to move while they run, and they’re big enough to fall under EPA’s pollution standards for turbines. In her words, that makes them “stationary combustion turbines” – and not mobile sources.

Then she got to MDEQ’s letter. Her ruling calls Mississippi’s air rules the SIP – short for state implementation plan. It’s basically Mississippi’s own federally approved air rulebook.

“Since MDEQ’s letter to the defendants is not consistent with Mississippi’s SIP, the letter does not alter the Court’s determination that the defendants’ turbines are not mobile sources.”

She also said the court doesn’t have to take MDEQ’s word for what that rulebook means – “Under Mississippi law, courts do not give deference to agency interpretations of statutes.”

Then she took on the “temporary” half of the letter, in a footnote – “It is unclear why the length of time the turbines remain on-site is relevant to permitting requirements.”

In plain words, she couldn’t see why it matters how long a turbine sits there.

Mississippi’s own Attorney General, Lynn Fitch, filed a brief on the companies’ side in July, and even it told the court that MDEQ’s decision “does not purport to apply a standalone exemption for ‘temporary’ sources.” The State’s view is that the twelve months was just evidence the turbines were mobile. I covered that brief on October 1st.

And MDEQ told me in writing on September 15th that it keeps no records tracking those twelve months – not by unit, not by group, and not by site. Its inspectors did go out to the site on September 14th.

Her bottom line was that the plant “was not (and is not) exempted from permitting requirements.”

Now, the judge wasn’t the first one to read the rules this way. The turbine industry beat her to it.

On December 8th, 2025 – about four months after MDEQ’s letter – a group called the Coalition of Mobile Electric Turbine Users asked EPA to change the rules. It goes by COMET. I wrote about its petition in September, after EPA answered my records request.

COMET wanted portable turbines treated like the generators you’d see on a job site, with no air permit needed. You don’t ask to change a rule that already says what you want.

And COMET’s own petition says what the rule says now – “Because portable combustion turbines are a ‘stationary source’ under the regulatory framework, they trigger state stationary source permitting programs.”

A few pages later, it says those programs “require preconstruction approval.” That means you get the permit before you build the thing.

COMET’s chair works for Life Cycle Power, a portable turbine company. Life Cycle Power supplies the M35 turbine, and the NAACP’s complaint lists one M35 among the machines at Southaven.

Less than a year after that petition, a federal judge read Mississippi’s rules the same way.

Before anybody gets ahead of this – it was a ruling on xAI’s motion to throw the case out. At this stage, a judge has to take the NAACP’s facts as true. She didn’t find that xAI broke the law.

The ruling doesn’t shut anything down or set any fine.

The NAACP is asking for penalties of up to $124,426 a day for each violation, and an order that the plant follow the Clean Air Act. None of that has been decided yet. Its request to turn the turbines off is still waiting on the same judge.

The judge also wrote that “MDEQ fairly notified the defendants of its interpretation.” In other words, the state told xAI in writing that it didn’t need a permit – and that’s the defense xAI’s lawyers raised. She also wrote that “MDEQ is not attempting to impose civil liability against the defendants.”

But there’s one more footnote.

“If MDEQ were to now assert that the defendants needed a permit after previously determining they did not, that would create a fair notice issue.”

Fair notice basically means you can’t punish somebody for doing what you told them was fine. So if MDEQ tried to say now that a permit was needed all along, the judge says it would run into that problem – because it’s the agency that wrote the letter.

The judge said the NAACP doesn’t have that problem – the state’s notice “does not mean that the plaintiffs are barred from bringing this action.”

On November 4th, Jan Schaefer, MDEQ’s communications director, gave the news site Mississippi Today the agency’s answer – “MDEQ is not a party to that case and the order is not binding upon the agency. Furthermore, that litigation is ongoing and subject to appeal so it is not final at this point.”

All of that is true. MDEQ isn’t a party to the case, and the case isn’t over.

But the statement doesn’t say whether MDEQ still thinks its letter was right.

Mississippi’s Permit Board – the panel that votes on the state’s permits – is holding a hearing in Jackson on November 9th and 10th. It’s about a different permit, for a permanent gas plant MZX is building on the same land, and the NAACP and two local groups are appealing it.

The NAACP’s complaint says none of the trailer turbines are in it – I went through that on October 1st.

I’ve also asked MDEQ whether any of the other sites xAI’s company is planning in Southaven got letters like this one.

In September I wrote that even if a ruling went against xAI, it wouldn’t shut down either of xAI’s Memphis data centers.

This ruling went against xAI. Nothing in it turns a single turbine off.

So who decides whether a turbine on a trailer needs a permit in Mississippi? MDEQ said no. A federal judge says yes. And MDEQ says her order doesn’t bind it.

So, who the hell is in charge here?

Sources

Every record below is also on the records page for this essay.

The xAI files

Sources

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