Comment 21 for bug 205496

A better way to do it is to add "scanner" to your user's groups (in teh
user control panel, giver scanner permissions), however, udev creates
the scanner device with the owner:group root:root, when it should have
been "root:scanner".

The solution is to add your user to the scanner group, then find what
bus your USB scanner is on with "lsusb" (you get a number like 002:004),
then

sudo chown root:scanner /dev/bus/usb/002/004 (or what ever the numbers are)

I have to do this every time I plug in the scanner, or turn on the computer.