Dynamic React feature flags enable developers to control user access to specific application features based on conditions such as user roles, location, or relationships to resources. This guide details implementing a feature toggle system using CASL, a JavaScript authorization library, and Permit.io to manage permissions through Relationship-Based Access Control (ReBAC). The tutorial demonstrates building a document management app where user permissions to create, view, or edit documents are determined by their relationships to the resources. By leveraging ReBAC, developers can dynamically adapt feature visibility and actions, allowing for a more granular and flexible approach compared to static Role-Based Access Control (RBAC). The guide emphasizes setting up a local Policy Decision Point (PDP) for real-time access decisions, integrating CASL for granular permissions, and using the permit-fe-sdk to efficiently load and check permissions. This method allows developers to personalize user experiences and manage permissions without modifying the underlying code, enhancing security and adaptability in complex use cases.