Problem Definition

It is not possible to update or edit page restrictions through the Confluence API.

This is possible in Confluence Cloud, per the Confluence Cloud API documentation.

Suggested Solution

Implement a similar method/endpoint for the Confluence Server API.

Why this is important

If administrators need to update a large number of page restrictions, the REST API would be helpful for automating some of this work.

Workaround 

The Bob Swift Confluence CLI can achieve this objective.