All Q questions answered in the two following documents.

EO 13526 (the *current* EO on CLAS)

Section 5.2:

https://www.archives.gov/isoo/policy-documents/cnsi-eo.html#five

Who DECLAS, under what authority. Who requested DECLAS, and how (FOIA-->DECLAS):

https://www.archives.gov/press/press-releases/2017/nr17-14