CONTINUED ACCESS TO CLASSIFIED INFORMATION
Whether or not former officials keep their eligibility and access to classified information is another issue more grounded in tradition than policy. It is common for outgoing presidents and officials to be ‘read in’ on issues and topics where their prior position and expertise are useful. This is at the discretion of the current sitting president. That means that any access to classified information a former president or government official obtains has to be granted – they can’t just walk into the CIA and say ‘brief me.’
https://news.clearancejobs.com/2020/11/30/former-presidents-and-eligibility-to-access-classified-information/