There is a configuration setting on Workflows for Availability called Depending on User Status.
Depending on User Status
Select this option to enable Workflows on the Self Service or Helpdesk sites according to the user status.
If the user’s Questions and Answers profile is locked, then no workflows are enabled on the Self-Service site, and the user should contact their local Helpdesk.
The following is the default criteria for enabling and disabling workflows on the Helpdesk site: