FAR 4.1102(a) provides the policy regarding the registration in SAM, and DFARS 204.1103 and DFARS PGI 204.1103 provide the procedures for DoD. Provision 52.204-7 provides the requirements to offerors as to what is required for SAM. The bottom line with all of these references is that subcontractors do not require an active CAGE and SAM registration. To better understand SAM, check out the below link. 

https://www.federalregister.gov/documents/2018/09/26/2018-20706/federal-acquisition-regulation-system-for-award-management-registration