The place that performs the action should be able to say no

A policy service can approve a request. A model can classify it. A workflow can carry it. But if the tool that performs the side effect cannot refuse the action, the rest of the system is advisory.

Enforcement has to exist at the point where the effect happens. The system that sends, deletes, spends, or changes the record should validate the authority it received. Otherwise the policy exists somewhere in the diagram, but not where it matters.

Central policy still has value. It can keep decisions consistent and understandable. The final boundary simply needs its own ability to reject a request that does not carry valid authority.

A control that cannot stop the action is documentation.