<p>Power BI developers manage user access and security by implementing role-based security models within Power BI. They use row-level security (RLS) to restrict data access, ensuring that users only see data relevant to their roles or departments. Power BI developers create security groups and assign them to specific dashboards or reports, allowing for controlled access based on user needs. Additionally, developers monitor and audit user activity, set up permissions, and ensure data compliance with organizational policies or legal regulations like GDPR, keeping sensitive data protected and secure.</p>