If no one with clearance can now share their intelligence with him we should watch him closely to see if he slips up and reveals something he’s not supposed to know.
Since he is a private citizen with no clearance now, the violation, if I understand the rules, falls, not on him, but on the person who disclosed the information to him.
Still, Mr. Brennan will not be idle as slinging insults at the President seems to be much more interesting to him anyway.