# NIST SP 800-53 Rev. 5 SC-46 — Cross Domain Policy Enforcement - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-46-cross-domain-policy-enforcement - Section: [Compliance](https://support.icompaas.com/compliance) › [NIST SP 800-53 Rev. 5 Controls](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5) › SC — System and Communications Protection - Last updated: 2026-06-05 - Publisher: iCompaas, Inc. (https://www.icompaas.com) **NIST SP 800-53 Rev. 5**·Control `SC-46`·critical·Component: **System and Communications Protection** ## What this control requires > Implement a policy enforcement mechanism, either physically or logically, to govern the connections between security domains. Logical policy enforcement prevents the creation of paths that could bypass the control, while physical enforcement ensures strong isolation between domains, preventing covert channels from penetrating the security boundaries. This control supports the Policy enforcement, security domain isolation capability within the System and Communications Protection family. > > — NIST SP 800-53 Rev. 5, Control SC-46 ### In plain English Implement a policy enforcement mechanism, either physically or logically, to govern the connections between security domains. In practice, this means you can prove you policy management-level controls on a defined cadence. ## Why it matters SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed. This control is rated **critical** in the source catalogue. Treat gaps here as production incidents in the risk register, not housekeeping. ## What an auditor looks for A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan. Within **System and Communications Protection**, the assessor will trace your implementation back to the catalogue reference (Control SC-46) and look for objective evidence on the latest two assessment cycles. ## How to implement #### Physical Security **Inheritance.** For cloud-only operations, inherit physical controls from the provider's SOC 2 / ISO 27001 report and document the inheritance in the SoA. #### Policy Management **Docs.** Keep each policy in version-controlled Markdown alongside the code that implements it; ship a signed PDF snapshot at each annual review and link the SHA into the SoA. ### Operational checklist - **Policy.** Document the trigger, the owner and the cadence. - **Security.** Document the trigger, the owner and the cadence. - **Domain.** Document the trigger, the owner and the cadence. - **Physical.** Document the trigger, the owner and the cadence. - **Protection.** Document the trigger, the owner and the cadence. - **Scope:** management, enforcement, domains, system, protection, capability, security policy, implement. ## Evidence to collect - **Policy Document.** A signed and version-controlled policy / standard / procedure document. Signed policy or standard documents the safeguard. Focus: Cross Domain Policy Enforcement. ## Common pitfalls - Policies that no engineer has read; the version in Confluence drifts from the version that's actually being enforced. ## How it maps to other frameworks Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit. - [**NIST SP 800-171 Rev. 3 3.14.3** — Security Alerts, Advisories, and Directives](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-14-3-security-alerts-advisories-and-directives) - [**ISO/IEC 27001:2022 A.7.3** — Securing offices, rooms and facilities](https://support.icompaas.com/compliance/iso-27001-2022/a-7-3-securing-offices-rooms-and-facilities) - [**HIPAA (45 CFR Part 164) 164.308(a)(5)(i)** — Security Awareness and Training](https://support.icompaas.com/compliance/hipaa/164-308-a-5-i-security-awareness-and-training) - [**BSI C5:2020 SP-01** — Documentation, communication and provision of policies and instructions](https://support.icompaas.com/compliance/bsi-c5-2020/sp-01-documentation-communication-and-provision-of-policies-and-instructions) ## Related controls in NIST SP 800-53 Rev. 5 - [**Control SC-39(2)** — Separate Execution Domain Per Thread](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-39-2-separate-execution-domain-per-thread) - [**Control SC-36** — Distributed Processing And Storage](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-36-distributed-processing-and-storage) - [**Control SC-49** — Hardware-Enforced Separation And Policy Enforcement](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-49-hardware-enforced-separation-and-policy-enforcement) - [**Control SC-31(1)** — Test Covert Channels For Exploitability](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-31-1-test-covert-channels-for-exploitability) - [**Control SC-50** — Software-Enforced Separation And Policy Enforcement](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-50-software-enforced-separation-and-policy-enforcement) - [**Control SC-3(5)** — Layered Structures](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-3-5-layered-structures) ## References - [NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5](https://csrc.nist.gov/Projects/risk-management/sp800-53-controls) - Catalogue identifier: `Control SC-46` Topics: governance riskphysical securitypolicy management ## Related compliance guidance - [NIST SP 800-53 Rev. 5: a practical implementation guide for cloud teams](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5): Start with the full NIST SP 800-53 implementation guide — scope, roadmap, evidence and how the assessment runs. - [NIST SP 800-171 and CMMC: a practical guide to protecting CUI in the cloud](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3): If your obligation is protecting CUI in your own systems for a federal or defence contract, this derived subset — not the full catalogue — is the requirement. - [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Most commercial SaaS already hold a SOC 2 Type 2, and FedRAMP 20x Class A is designed for providers that have one.