On Monday, President Donald Trump and his son, Donald Trump Jr. retweeted a viral video that claimed hydroxychloroquine was a cure for the coronavirus. Twitter removed the video and limited “some account functionality for 12 hours” for Trump Jr.

Liz Kelley, a spokesperson for Twitter, said that the tweets were “in violation of our COVID-19 misinformation policy.”

The video in question showed a group of doctors from the “America’s Frontline Doctors” in a press conference before the U.S. Supreme Court. It was published by Breitbart News, a right-wing media outlet known to have published conspiracy theories and misinformation.

In the video, a female doctor claims, “This virus has a cure, it’s called hydroxychloroquine, zinc, and Zithromax. You don’t need masks, there is a cure.”

America’s Frontline Doctors also stated that lockdowns were unnecessary.

Hydroxychloroquine is an antimalarial drug that Trump touted as a potential solution for COVID-19, though the Centers for Disease Control and Prevention says there is currently no specific antiviral treatment for COVID-19. In June, the New England Journal of Medicine reported that hydroxychloroquine had no significant effect on the coronavirus compared to a placebo treatment, though it did cause stomach problems as a side effect. Others report that fatal heart arrhythmia and elevated liver-enzyme levels correlated with hydroxychloroquine treatments.

A spokesman for Trump Jr., Andy Surabian, said that Twitter’s response was “further proof that Big Tech is intent on killing free expression online and is another instance of them committing election interference to stifle Republican voices.”

Twitter stated in March that they were “expanding [their] safety rules to include content that couple place people at higher risk of transmitting COVID-19.” They included a list of content that would be removed, such as denial of expert guidance, encouragement to use fake or ineffective treatments, preventions, and diagnostic techniques, and misleading content purporting to be from experts or authorities.