Policies solve the distribution problem of standards: rules pasted into system prompts drift as prompts are copied and edited, and rules in a handbook are wherever the agent is not. A policy lives in one place, is assigned to the workflows it governs, and arrives inside the active step's payload.
The operational consequence is instant propagation: edit the policy once and every run in flight picks it up at its next step. No template surgery, no redeploy, no memo.
Policies inform; they do not block. The blocking primitive is the gate. A governance design that is honest about that split puts rules in policies and stop-points in gates, and never claims one does the other's job.