Hi Steve,
Since this task needs to be accomplished for a specific user. You can do the following:
1-Create a command set for this specific user to allow/deny the required commands on the following section "Policy Elements > Authorization and Permissions > Device Administration > Command Sets."
2-Create a rule using username as condition as you can see on the bellow example to assign Read only command set as you can see on the example attached ( please make sure to move this rules at the very top of from the other rules you might have configured, as this is very specific).
Note: Please marked as answered if applicable