Most recently, Brennan condemned Trump’s recent attacks against former aide Omarosa Manigault Newman, who the president called a “lowlife” and a “dog” after she wrote an inside account of her time in the White House.

“Seems like you will never understand what it means to be president, nor what it takes to be a good, decent, & honest person,” Brennan tweeted Tuesday, directly addressing Trump.

It’s astounding how often you fail to live up to minimum standards of decency, civility, & probity. Seems like you will never understand what it means to be president, nor what it takes to be a good, decent, & honest person. So disheartening, so dangerous for our Nation. https://t.co/eI9HaCec1m

— John O. Brennan (@JohnBrennan) August 14, 2018

Press Secretary Sarah Sanders, who announced on Wednesday that Brennan’s security clearance had been revoked, also named other current and former officials that Trump may target with clearance removals—most of whom have been Trump critics. The list includes former FBI Director James Comey, former National Security Advisor Susan Rice, former FBI agent Peter Strzok, former FBI lawyer Lisa Page, and Justice Department official Bruce Ohr, among others.

Former high-ranking officials typically retain their security clearances after leaving their position so they can advise those still working in the government, or pursue work with security contractors. Per a report by the Office of the Director of National Intelligence, over 4 million individuals held a security clearance as of October 2016.

Revoking a former official’s security clearance can hinder their ability to get a job in a related market, but does not stop them from criticizing the administration publicly.

According to The New York Times, Sanders denied that the individuals were chosen based on their criticism of the president. She said that Brennan’s security clearance was lifted because of allegedly “erratic conduct and behavior,” the nature of which she did not detail.