I'd like to restrict access (at least editability) to issues that are in the product backlog and not yet pulled into a sprint. I have a Product Backlog Kanban board in my project with statuses Backlog, Story Prep, Refinement, and Defined. Separately, we have a Scrum Board for statuses starting at Sprint Backlog through Dev, QA, documentation, PO Review, and Done.
I'd like to make sure that the only person who can make edits while an issue is in the Product Backlog statuses is the Product Owner. So I'd either like to restrict access to that board or make issues read-only for everyone except the PO until the issue makes it to Sprint Backlog status.
What are the best way(s) to do that?