It was also a significant public-relations gambit. Schneiderman seized the moment to share the fact that he had issued a subpoena to Exxon and that he was investigating the company. “We are pursuing this as we would any other fraud matter,” he said. “You have to tell the truth. You can’t make misrepresentations of the kinds we’ve seen here.” Maura Healey, the Massachusetts attorney general, announced that she, too, had joined Schneiderman in investigating Exxon, along with the attorneys general of California and the U.S. Virgin Islands. “We can all see today the troubling disconnect between what Exxon knew, what industry folks knew, and what the company and industry chose to share with investors and with the American public,” Healey said. (My colleague Abigail Tracy has reported on Healy’s own potential political future.)

Al Gore, the former vice president and the recipient of the Nobel Peace Prize for his work on raising consciousness about the problem of climate change, was also at the press conference to reiterate the importance of Schneiderman’s investigation. “I really believe that years from now this convening by Attorney General Eric Schneiderman and his colleagues here today may well be looked back upon as a real turning point in the effort to hold to account those commercial interests that have been—according to the best available evidence—deceiving the American people, communicating in a fraudulent way, both about the reality of the climate crisis and the dangers it poses to all of us,” he said. “And committing fraud in their communications about the viability of renewable energy and efficiency and energy storage that together are posing this great competitive challenge to the long reliance on carbon-based fuels.” Gore said the work of the state attorneys general was “the best, most hopeful step I can remember in a long time.”

Schneiderman’s dramatic press conference occasioned a drastic change in ExxonMobil’s behavior. The company began a public-relations campaign of its own designed to discredit the premise of his investigation via a flotilla of high-priced lawyers, communications specialists, powerful U.S. congressmen, and other state attorneys general. In May 2016, Texas Congressman Lamar Smith, the chair of the House Committee on Science, Space, and Technology—and the recipient of some $20,000 in campaign contributions from Exxon since 2008—wrote a letter to Schneiderman informing him that his committee had opened an investigation into both Schneiderman and Healey because his tactics “amount to an abuse of prosecutorial discretion.” He demanded four years worth of records and correspondence from Schneiderman and Healey as well as from various environmental activists, such as the Union of Concerned Scientists and 350.org, environmentalist Bill McKibben’s organization. The objective, it seemed, was to try to chill the investigation and the support for it from environmental activists.

Months later, Exxon sued both Schneiderman and Healey in federal court in Texas. (Schneiderman called this move “unprecedented” since “it is established law” that subpoena disputes are adjudicated in state courts.) In its amended complaint, filed in November 2016, Exxon sought an “injunction” against the two attorneys general seeking to bar the enforcement of the subpoenas. Exxon argued that the attorneys general were in the process of conducting “improper and politically motivated investigations of ExxonMobil in a coordinated effort to silence and intimidate one side of the public-policy debate on how to address climate change.”

In a fascinating twist, Exxon argued that Schneiderman and Healey were violating the company’s First Amendment right to free speech; it was entitled, it believed, to have its own views on climate change, regardless of who disagreed. Exxon wrote that “for more than a decade” it had “widely and publicly confirmed” that it “recognize[s] that the risk of climate change and its potential impacts on society and ecosystems may prove to be significant.” Since 2009, the company document stated, it had “advocated” for a tax on carbon emissions and had estimated what it called a “proxy cost of carbon,” of as much as $80 per ton by 2040 as a way to convey to shareholders, employees, and the public that it was accounting publicly for the costs of climate change. “It is now indisputable that the subpoena and the [civil investigative demand] were issued in bad faith to deter ExxonMobil from participating in ongoing public deliberations about climate change and to fish through decades of ExxonMobil’s documents in the hope of finding some ammunition to enhance the coalition’s, and its climate activist confederates’, position in the policy debate over climate change,” the company asserted.

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Not long after Tillerson was sworn in as Trump’s secretary of state, the Texas judge decided to transfer the case to the Southern District of New York. “I have a very different view of this case than [the judge in Texas],” said Valerie Caproni, the presiding federal judge in New York. Since then, Schneiderman has been winning most of the legal battles in the New York and federal courts, despite Exxon’s ongoing efforts to thwart his investigation. He defeated Exxon in its attempt to prevent PricewaterhouseCoopers, its accounting firm, from turning over to him documents requested under a second subpoena. These documents detailed Exxon’s reporting on oil and gas reserves, the evaluation of its assets for potential impairment charges or write-downs as well as for projected carbon cost estimates. Schneiderman is now getting documents from PricewaterhouseCoopers, “which is very good,” he told me. He won the right to depose an Exxon employee at its Canadian affiliate, Imperial Oil, despite Exxon’s efforts to prevent Schneiderman’s access to him.