The group of young people suing the federal government for failing to protect their constitutional right to a stable climate is seeking testimony in their landmark case from Rex Tillerson, CEO of ExxonMobil and President-elect Donald Trump’s nominee for secretary of state.

Attorneys representing the 21 young people in their federal climate lawsuit served the notice of deposition (pdf) on Thursday, demanding Tillerson’s testimony on January 19, 2017 in Dallas, Texas. They claim that “[a]s CEO of ExxonMobil, Tillerson has unique personal knowledge of the fossil fuel industry’s historical relationship with the federal government.”

What’s more, they add, Tillerson and Exxon have been leaders in the American Petroleum Institute (API), National Association of Manufacturers (NAM), and American Fuel and Petrochemical Manufacturers (AFPM)—the trade associations that joined the federal climate lawsuit as defendants. “Tillerson serves on the board of API and he and other Exxon executives also serve on the board of NAM,” reads a statement from Our Children’s Trust, the non-profit supporting the legal action. “The youth plaintiffs seek to prove these trade associations have known about the dangers of climate change since the 1960s and have successfully worked to prevent the government from taking the necessary steps to fully address climate change.”

Exxon is at the center of a campaign that seeks to hold Big Oil accountable for suppressing evidence and funding denial of climate change. Climate groups have vowed to grill Tillerson on Exxon’s climate fraud at his confirmation hearing in January.

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