Comment 52 for bug 433654

Actually the problem is more general and it regards permissions to access certain devices (and files in /dev directory). Historically if a user needs access to particular device he is assigned to a group which group-owns the device file. It has worked for ages in the unix world i.e. access to an audio device, cdrom, cd burner etc.

This group based approach has several well known limitations. Now it seems that such an access is controlled by consolekit/policykit/udev, which makes some sense, at least because of the dynamic nature of /dev directory. The gnome-system-tools and especially users-admin seem not to know anything about acl. I'm not sure whether it's good or bad - it depends, espoecially that gnome is cross platform - on other systems /dev might be static or there might be no acl at all. So I guess it should be up to the ubuntu team to keep the group assignments and acl sane and well documented, and the entire mechanism clear. Unfortunatelly I haven't found any explanation of it :( in the documentation. Perhaps a good idea it is to start a thread about it in the ubuntu formums. However, in my opinion, such a big thing as device access policy should be officially documented - not reverse engineered!