Newsweek reports:

Quote
In pursuing the unprecedented search of Donald Trump's residence on Monday, the FBI was seeking to retrieve Top Secret and "compartmented" documents dealing with intelligence "sources and methods," two federal government sources tell Newsweek—documents with the potential to reveal U.S. intelligence sources, including human sources on the American government payroll.

This greatly complicates any public discussion of the documents or any substantiation of Trump's potential violation of U.S. law. The sources, who were briefed on the investigation, requested anonymity in order to discuss sensitive information.

"Compartmented" is a specific term meaning "classified information concerning or derived from intelligence sources, methods, or analytical processes, which is required to be handled within formal access control systems established by the Director of National Intelligence." It includes a variety of different access categories—for example, human, intercept, satellite sources—each of which limits how many people can know the nature of the compartment.

How much value is that to Vlad Putin or Prince Bone Saw?

Contrarian, extraordinaire