The Virgin Islands attorney general has withdrawn a controversial subpoena against a prominent libertarian D.C. think tank, after being accused of bullying the group as part of a broader probe into whether ExxonMobil misled the public about global warming. 

Attorney General Claude Walker had issued the subpoena, demanding the Competitive Enterprise Institute hand over 10 years' worth of its communications related to climate change, in April.

CEI fired back with a lawsuit of its own, seeking to fine Walker for what the group called a breach of their First Amendment rights.

Walker's office dropped the subpoena Friday, according to court documents. The office did not respond to a request for comment from FoxNews.com.

CEI said it would still seek sanctions against Walker -- noting that while this subpoena has been dropped, a more expansive subpoena against ExxonMobil still stands.

“CEI is going forward with our motion for sanctions because Walker's withdrawal only strengthens our claim that this subpoena was a constitutional outrage from the very beginning, violating our right to free speech and our donors' right to confidentiality, and threatening the right of all Americans to express views that go against some party line,” CEI General Counsel Sam Kazman said in a statement. 

The probe into whether Exxon misled the public on the risks of global warming is itself part of a broader battle against the oil giant by a coalition of attorneys general, led by New York’s Eric Schneiderman, and environmental groups.

The coalition claims Exxon lied about the risks of climate change, similar to the way tobacco companies misled the public about the risks of smoking.

Walker’s subpoena against Exxon seeks 40 years' worth of communications with 90 conservative groups, including CEI, “and any other organizations engaged in research or advocacy concerning Climate Change or policies.”

Last week, Texas Attorney General Ken Paxton and Alabama Attorney General Luther Strange asked a Texas state judge to put an end to Walker's investigation, calling it “a fishing expedition of the worst kind.”

“This case is about abusing the power of the subpoena to force Exxon to turn over many decades’ worth of records, so an attorney general with an agenda can pore over them in hopes of finding something incriminating,” Paxton said in a statement. “[It] ... represents an effort to punish Exxon for daring to hold an opinion on climate change that differs from that of radical environmentalists.”