Cannot deleted from Project Roles using REST API

Summary

Deleting Role-Actor per the API Documentation listed here:

• API Documentation Delete Actor

Additional Note on Syntax: https://jira.atlassian.com/browse/JRA-43999

DELETE http://<BASE_URL>/rest/api/2/project/{projectIdOrKey}/role/{roleID}?user='user_name'
OR
DELETE http://<BASE_URL>/rest/api/2/project/{projectIdOrKey}/role/{roleID}?group='group_name'

Will Produce a 204 successful event but the user/group is not removed if they are associated to an external read only directory

Environment

• REST API for JIRA server 7.0.X +

Steps to Reproduce

1. Connect JIRA to an external LDAP directory as Read only
2. AddExternal user to A project Role
3. Attempt to delete the user from the role via API
4. Receive Status 204 Returned if the actor was successfully removed from the project role.

Expected Results

User is no longer associated to the Project Role

Actual Results

User is still associated to the role

Notes

The opperation completes successfully with the same external user in the Web UI
the API operation completes successfully for users in the internal user directory directory ID=1

Workaround

Modify the Project Role for users in an external directory from the project settings in the Web Interface