18 U.S. Code § 1924 - Unauthorized removal and retention of classified documents or material
https://www.law.cornell.edu/uscode/text/18/1924
Yeah, but the language includes knowingly.
Therefore, I imagine that if the matter ever comes to a trial, Hillary and her counsel will be able to convince a Washington DC jury of her "peers" (read "fellow liberals") that she didn't "know" what was classified and what was unclassified. So the jury will let her go scot free.
Now of course, you and I realize that her not "knowing" about classification requirements makes her totally unqualified to hold and enjoy any Office of honor, Trust or Profit under the United States. But it remains to be seen whether 51% of the American electorate will ever care about such arcane details