We have gone through a couple of JIRA upgrades and found that legacy users' user-groups are not modifiable.
It allows the action but does not reflect the removal after the action is completed.
This issue still persists in our JIRA 5.1 test environment with backup data.
- using a downloaded instance of JIRA
- tested on 4.3.2, 5.1, 5.1.3, 5.1.4 versions of JIRA
- system administrator privileges
- using Active Directory authentication
- applies to users that have been disabled via Active Directory at one point (not necessarily disabled now)
- existing groups prior to being disabled are no longer removable (applies to user being both enabled or disabled in Active Directory)
- new groups can be added and removed