The Re-open request button is currently configured at the workflow level. It becomes enabled if the following states are satisfied:
1. Request has closed or cancelled status 2. The user has privilege to edit the Request (actually PPM doesn't have a specific access grant for the reopen request option) 3. The workflow is configured to have a Re-open step
Currently the application doesn't have an option to restrict (access grant) a specific set of users to perform the reopen action. There are no access grants affecting directly on this function. More than the Edit Request access grant, so if they are able to Edit Request, they can click in the button.
There is a product Enhancement raised for it: QCCR1L41554-- Enhancement to create a new security access grant called REOPEN REQUESTS to further control requests reopening