A federal judge in Texas is allowing ExxonMobil to depose Massachusetts Attorney General Maura Healey in Dallas next month regarding a wide-ranging investigation of the supermajor. New York’s Eric Schneiderman also was told to make himself “available” for testimony on Dec. 13.

The order by U.S. District Judge Ed Kinkeade of the Northern District in Forth Worth regards a counter lawsuit filed by ExxonMobil following a multi-state investigation launched last year by Schneiderman. The state AGs are probing whether ExxonMobil violated securities laws and consumer protection regulations. Also being investigated is whether the supermajor properly accounted for its oil and natural gas reserves.

ExxonMobil retaliated with a lawsuit first against Healey and amended it last week to add Schneiderman. The company is accusing them of “improper bias and unconstitutional objectives” (ExxonMobil Corp. v. Healey, 16-cv-00469).

ExxonMobil has asked Kinkeade to impose an injunction to prevent subpoenas from being enforced, which demand years of internal research and investor communications. It argues that the AGs are pursuing a political agenda aligned with anti-fossil groups.

The AGs are “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,” ExxonMobil’s lawsuit states.

“We have no choice but to defend ourselves against politically motivated investigations that are biased, in bad faith and without legal merit,” spokesman Alan Jeffers said. “We did not start this, but we will see it through and will vigorously defend ourselves against false allegations and mischaracterizations of our climate research and investor communications.”

Kinkeade’s order reinforces his October ruling granting discovery. The judge expressed concerns last month about whether Healey’s office was investigating ExxonMobil in bad faith. ExxonMobil also is seeking to bar enforcement of Healey’s civil investigation demand, which was filed in Massachusetts.

Kinkeade wrote that the court “is mindful of the busy schedule of each of the Attorneys General Healey and Schneiderman and will be open to considering a different date for the deposition” other than Dec. 13.

Healey is “vigorously opposing” Kinkeade’s order. During an event in Boston on Monday, Healey was asked by reporters if she planned to fight the order to appear in Dallas.

“Legally, we believe we’re on strong legal ground, not only with respect to the questions that we’ve asked but also with respect to the position that this court has no jurisdiction over us — meaning, in simple terms, what the court has done is inappropriate,” Healey told reporters.

The probe into ExxonMobil activity is not politically motivated, she said.

“Our position in this litigation is that the authorities in Texas, and specifically the federal court down there, has no jurisdiction over state attorneys general and the work of their offices, and it’s been disappointing to see Exxon fight requests for basic information,” she said. “Our job as attorneys general is to be able to ask questions, and when we become aware of instances of potential fraud — potential fraud on consumers — it’s our job to be able to ask questions, ask companies for information and have companies produce that information.”