Exxon Mobil Corp. went to court Wednesday to challenge a government investigation of whether the company conspired to cover up its understanding of climate change, a sign the energy company is gearing up for a drawn-out legal battle with environmentalists and officials on the politically charged issue.

The company filed court papers in Texas seeking to block a subpoena issued in March by the attorney general of the U.S. Virgin Islands, one of several government officials pursuing Exxon. Wednesday’s filing argues that the subpoena is an unwarranted fishing expedition into Exxon’s internal records that violates its constitutional rights.

“The chilling effect of this inquiry, which discriminates based on viewpoint to target one side of an ongoing policy debate, strikes at protected speech at the core of the First Amendment,” the filing says.

Exxon also dismisses the notion that there is any suggestion of a crime, saying Attorney General Claude Earl Walker “issued the subpoena without the reasonable suspicion required by law and based on an ulterior motive to silence those who express views on climate change with which they disagree.”

A request for comment to the U.S. Virgin Islands’ attorney general’s office wasn’t immediately returned.