Intelligence Community Policy Guidance 404.1: Federal Partner Access to Intelligence Community Information Technology Systems, June 16, 2017 [open pdf - 3MB]
"This Intelligence Community Policy Guidance (ICPG): 1. Defines the process for Executive agencies or departments that do not contain an embedded Intelligence Community (IC) element, hereinafter referred to as Federal Partners, to access IC information technology (IT) systems containing Sensitive Compartmented Information (SCI) in accordance with Intelligence Community Directive (ICD) 404, 'Executive Branch Intelligence Customers'."
Intelligence Community Policy Guidance 404.1
Office of the Director of National Intelligence: http://www.dni.gov/