On Thursday, dozens of doctors and researchers from Stanford University emphasized that they won’t be silenced after hearing they may face legal action after criticizing the White House’s coronavirus advisor Dr. Scott Atlas. 

Earlier this month, Stanford academics penned an open letter calling out Atlas, a former colleague, for spreading what they characterized as “falsehoods and misrepresentations of science.” In particular, the authors expressed concern about Atlas advocating against the use of masks and other public health measures.

In response, the researchers behind the “Dear Colleague” letter said they received a legal threat on Sept. 16 from Marc Kasowitz of the law firm Kasowitz Benson Torres, which asked the letter writers to withdraw their claims or face legal action. Kasowitz claimed to represent Atlas, who currently works as a senior fellow at Stanford University’s Hoover Institution.

Atlas, in his medical career, has specialized in radiology and neuro-radiology and not infectious disease.

In recent months, he’s made a series of controversial statements, including to push the White House to allow young people to contract the coronavirus in hopes of achieving “herd immunity.”

A copy of Kasowitz’s letter was posted on Twitter by Michael Fischbach, a Stanford professor. In addition, a spokesperson for the Stanford faculty who penned the letter shared a copy of with CNBC.

Kasowitz’ letter describes the Stanford group’s criticisms as “abjectly false.” 

“We therefore demand that you immediately issue a press release withdrawing your letter and that you contact every media outlet worldwide that has reported on it to request an immediate correction of the record,” it reads. 

Fischbach, an associate professor in the department of bioengineering, tweeted in response: “I stand by everything we said.”

Following the legal threat, a larger group from Stanford University has now signed another letter stating that they will not be intimidated or silenced. 

“We believe that his statements and the advice he has been giving fosters misunderstandings of established science and risks undermining critical public health efforts,” reads the letter, which was signed by 105 doctors, scientists, public health experts and faculty members. 

“In addition, we are deeply troubled by the legal threats that Dr. Atlas has made against us in an attempt to intimidate and silence us in the midst of a pandemic.”

The group also sent their own letter defending their position from the firm Kaplan Hecker & Fink, which was addressed to Atlas’ legal team.