The company owned by billionaire conservative activist brothers Charles and David Koch has rejected Senate Democrats’ request for information about climate change research funding—an inquiry the legislators sent to fossil fuel industry players in the wake of a cash-for-analysis scandal.

A response to the letter from a Koch Industries Inc. lawyer struck a defiant tone, describing the request as an infringement on free speech.

“To the extent that your letter touches on matters that implicate the First Amendment, I am sure you recognize Koch’s right to participate in the debate of important public policy issues and its right of free association,” Mark Holden, Koch senior vice president and general counsel remarked.

The riposte was reported late Tuesday night by the Associated Press. A spokesperson for Sen. Ed Markey (D-Mass.), one of the Democratic lawmakers who asked for the information alongside Sens. Barbara Boxer (D-Calif.) and Sheldon Whitehouse (D-R.I.), told the AP that companies “supporting legitimate, scientific inquiry should have no concerns about responding.”

The free speech defense offered by the Kochs sidesteps the fact that some government-funded activities are at the heart of the matter.

The senators’ probe was sparked last month, after Greenpeace and the Climate Investigations Center revealed that an industry-funded Smithsonian Institution scientist, Willie Soon, was describing his published works, in private conversations with benefactors, as “deliverables.”

The Harvard-Smithsonian Center for Astrophysics scientist used the term to refer to both papers and Congressional testimony, the environmentalist activists found, after obtaining some of Soon’s emails through a Freedom of Information Act request.

The Smithsonian Institution is set to receive $819.5 million in federal appropriations this fiscal year. Only about one in ten scientists believe that climate change is not “mostly due to human activity.”

The First Amendment defense offered by the Kochs also obscures legal issues—namely that industry support of climate change deniers could be illegal, under federal civil statutes.

As Dan Zegart detailed in an April 2014 article in The Nation, some legal analysts “believe that fossil fuel producers could be vulnerable to fraud or civil conspiracy charges if it can be legally proved that companies…spent millions funding climate-change-denying organizations…while internally acknowledging that the science supporting anthropogenic (i.e., human-caused) climate change was a settled issue.”

“That could put Big Carbon in roughly the same position as Big Tobacco was in the early 1990s, when cigarette makers continued to cultivate public doubt about their product’s harmfulness long after they had accepted that it was addictive and deadly,” Zegart wrote.

Revelations that would emerge in any discovery process might turn the tide of public opinion against the fossil fuel industry, he also noted.

Soon received $230,000 from the Charles G. Koch Foundation and $324,000 in anonymous gifts funneled through a trust “used by the Kochs and other conservative donors,” The Guardian noted.

He also received $335,000 from ExxonMobil until 2010, and $274,000 from the American Petroleum Institute.