President Trump has revoked the security clearance of former CIA Director John Brennan due to "erratic conduct and behavior," according to White House Press Secretary Sarah Sanders at today's press briefing.

Why it matters: Sanders said that Trump was using his "constitutional authority" as president to revoke Brennan's clearance — something that has never been done before, according to Lawfare. Trump is also "evaluating action" regarding the current and former clearances of several other former intelligence and law enforcement officials like James Comey, James Clapper, Michael Hayden, Sally Yates, Susan Rice, Andrew McCabe, Peter Strzok, Lisa Page, and Bruce Ohr.

The timing: The decision comes one day after Brennan responded to Trump's infamous tweet calling former White House staffer Omarosa Manigault Newman a "dog" with a tweet of his own: "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."

Sanders denied that the decision to revoke Brennan's clearance was due to his continued political criticism of Trump, instead saying that he "recently leveraged his status as a former high ranking official with access to highly sensitive information to make a series of unfounded and outrageous allegations, wild outbursts on the internet and television about this administration."

What it means: Although most former officials will lose their physical access to classified material when they leave their government position, they maintain their eligibility for access — having passed extensive security clearances — for a few years, according to Lawfare.

Be smart: Ohr is still active in his role at the Justice Department and will need his security clearance not only for his day to day responsibilities but also for an interview with House Republicans slated to take place later this month.

Go deeper: What they're saying: Intel officials react to Trump's clearance threats.