A standoff between Elon Musk and Brazil escalated on Sunday when a Supreme Court judge opened an inquiry into the billionaire after Musk said he would reactivate accounts on the social media platform X that the judge had ordered blocked.

Musk, the owner of X and a self-declared free speech absolutist, has challenged a decision by Justice Alexandre de Moraes ordering the blocking of certain accounts. He has said X, formerly known as Twitter, would lift all the restrictions because they were unconstitutional and called on Moraes to resign.

Neither Musk, X nor Brazilian authorities have disclosed which social media accounts were ordered blocked. X first posted about the order to block on Saturday but it was not immediately clear when the order was issued.

Moraes is investigating “digital militias” that have been accused of spreading fake news and hate messages during the government of former far-right President Jair Bolsonaro and is also leading an investigation into an alleged coup attempt by Bolsonaro.