Why?
From their orientation page:
Protect the holdings of the National Archives from theft, damage, misfiling, and inappropriate disclosure of information.
Who knows, why should they feel obligated to supply any kind of rationale for their actions? [edit: /s]Here is the sum total of detail they have provided: “ All researchers must apply and present a researcher card, which may be obtained in Room 1000. This ensures that proper identification is on file for all individuals accessing the building to establish a legitimate business purpose. Abuse of any researcher registration to circumvent access by the general public may result in a trespass situation and a permanent ban from access to all NARA facilities.”
Staffing cuts, most likely: https://www.govexec.com/workforce/2025/06/trump-administrati...
So the administration can decide who gets to conduct research.
[flagged]
Abandon all hope, ye who seek reflective reasoning from this government.
But my guess is that less public access to national information helps, and does not hinder, a speed-run to autocracy.