Policy enforcement in Terraform means every change is checked against rules before it reaches production. It is the guardrail that keeps cloud resources in line with security, compliance, and cost requirements. Without it, admins rely on human review and hope. With it, every plan and apply runs through automated gates.
Using Terraform's native features, you can enforce policies with Sentinel or third-party tools. Sentinel lets you write policies in its own language and bind them to the Terraform workflow. For example, you can block any plan that creates unencrypted storage or that uses an unapproved region. These rules are tested with terraform validate or terraform apply hooks, stopping bad changes before they land.
Open Policy Agent (OPA) offers a more flexible path. Integrated with Terraform through tools like Conftest or directly in CI/CD pipelines, OPA uses Rego to define rich, versioned policies. It can enforce structure across Terraform configurations, reject resources, and log violations. OPA’s ecosystem connects easily to Kubernetes, APIs, and cloud-native services, letting you maintain a unified policy framework.