Per DoDI 5200.

DoDI 5200.48 specifies that Authorized Holders of CUI are responsible for applying appropriate CUI markings. An authorized holder is an individual who has lawful government purpose access to the information. This ensures that responsibility for correctly marking information rests with those who create or handle the material, not only with original classification authorities (which apply to classified information, not CUI).

Reference Documents:

DoDI 5200.48,Controlled Unclassified Information (CUI)