House Republicans are gearing up for their first congressional hearing on the investigation by Democratic state attorneys general into Exxon Mobil and climate change.

Rep. Lamar Smith, chairman of the House Science, Space and Technology Committee, said he would hold a Sept. 14 hearing. The Texas Republican has been busy subpoenaing the attorneys general of New York and Massachusetts over their Exxon investigations. The hearing is meant to demonstrate congressional authority to investigate the attorneys general.

The hearing was announced after weeks of back-and-forth between Smith and New York Attorney General Eric Schneiderman and Massachusetts Attorney General Maura Healey, both of whom have said Smith doesn't have the authority to conduct his investigation.

"The hearing will examine Congress' investigative authority as it relates to the committee's oversight of the impact of investigations undertaken by the attorneys general of New York and Massachusetts at the behest of several environmental organizations," a committee notice read.

"Specifically, the hearing will explore the validity of the committee's current inquiry in the context of Congress' broad oversight authority, as defined by legal precedent." The hearing will offer testimony from three conservative legal scholars to demonstrate that the committee's investigation "easily [falls] within Congress's legislative and oversight competence."

The attorneys general opened an investigation into news reports that showed Exxon in the 1970s had covered up its own scientists' data that showed the harm climate change posed to its business. They argue that by keeping the information from public view, the company committed a type of fraud. The company adamantly denies the allegations and in recent weeks has been successful in pushing back against the attorney general subpoenas.

Smith sent letters requesting information on the investigations to the attorneys general and affiliated environmental groups. He more recently began issuing congressional subpoenas after the attorneys general and activists refused to comply with the information request.

Smith and several of his committee's Republican members argue that the AGs' subpoenas of the oil giant represent an affront to free speech, meant to chill any debate on the issue of climate change.