A number of high-profile legal scholars have come to the defense of two state attorneys general and eight organizations in their refusal to comply with Congressional subpoenas seeking information related to investigations of ExxonMobil.

As part of an escalating confrontation between Rep. Lamar Smith and those spurring the investigations of Exxon in connection with its stance on climate change, the Texas Republican had hit the officials and non-governmental groups with subpoenas in July.

In a blunt letter Monday to Smith, the chairman of the House science committee, nine constitutional law scholars condemned the subpoenas as unlawful, unenforceable and "misguided." The letter was sent in advance of a Wednesday committee hearing on the issue.

The arguments reinforce those already articulated by the two attorneys general and several of the organizations when they told Smith they would not comply.

Smith did not respond to a call for comment.

Smith's subpoenas demanded documents related to discussions between the organizations and Attorneys General Eric Schneiderman of New York and Maura Healey of Massachusetts. The two states have opened investigations into Exxon over whether the oil giant misled investors or consumers on the risks of climate change.

Smith called the hearing to support the constitutionality of his subpoenas.

But the legal scholars, including Floyd Abrams, a high profile First Amendment attorney who defended the New York Times in the Pentagon Papers case, said Smith lacked the authority to issue the subpoenas.

"Your...subpoenas to the nine (sic) environmental organizations are invalid and constitutionally impermissible," according to the letter delivered Monday. "We urge you to withdraw them promptly."

Smith has defended the subpoenas by saying that the investigations of Exxon are depriving the company and its allies of their First Amendment rights to freely engage in science.

The legal scholars, citing three Supreme Court cases, turned the First Amendment argument on Smith.

"The Subpoenas, and the threat of future sanctions, themselves threaten the First Amendment—directly inhibiting the rights of their recipients to speak, to associate and to petition state officials without interference from Congress," according to the letter, which was drafted by the Abrams Institute for Freedom of Expression at Yale Law School.

The legal experts emphasized that the eight organizations subpoenaed have a track record of "contributing to a critical international effort to understand global climate change and to combat its causes."

The Union of Concerned Scientists was singled out in the letter as an example of one such group.

The organization was a member of the U.S. delegation that worked toward the Kyoto Protocol, a 1997 treaty to reduce greenhouse gas emissions. In the early 2000s, its climate experts played a key role in crafting the Regional Greenhouse Gas Initiative, the first multi-state effort to combat global warming.

The group continues its work worldwide in collaboration with more than 17,000 scientists and technical experts to develop and advocate for the adoption of solutions to the world's most pressing problems, according to the letter.

"The other organizations targeted with subpoenas have similar records of research and advocacy to promote informed environmental policy-making based on sound science," it said.

When those organizations discussed their concerns about Exxon's alleged distortion of climate science with state attorneys general and with each other, they were exercising their constitutional rights, the legal scholars told Smith.

"The First Amendment guarantees, among other rights, the rights to speak freely, to petition the government, and to associate with others for the advancement of beliefs and ideas," according to the letter.

The legal experts argue the subpoenas fail to meet the three tests required to validate Congressional subpoenas.

They must fall within Congress's general investigative authority, and the committee also must be authorized to issue the subpoenas. Further, there must be a compelling government interest in the information sought.

"Your committee's Subpoenas to UCS and the other environmental organizations meet none of these conditions and are patently improper," the scholars wrote.