Originally filed in fedora bugzilla. Also reproduced in Debian etch so bug must be in gnome:
https://bugzilla.redhat.com/show_bug.cgi?id=365091

Description of problem:
Option given to move files that are read-only [Can't be moved]

Version-Release number of selected component (if applicable):
2.18.3

How reproducible:
Always


Steps to Reproduce:
Nautilus allows users to try and move read-only files.
This shouldn't be allowed because:
1) Trying so will fail, and you will only achieve a copy operation.
2) It is impossible to move something that is read-only, because you can't delete it.

Try this:
Middle click a read-only file and drag to a writable folder.
Given options to copy, link, move, cancel.

The option to move should be disabled.

If I do try to move the file will copy and then I see this error dialog.
Error while moving.
"FILENAME" cannot be moved because it is on a read-only disk.
[Cancel Button] [Retry Button]

I don't know what the retry button is meant to do.
If nautilus knows that the file is on a read-only disk, why user to move it.
Is is already impossible to "cut" read-only files, moving operations should be the same.

The above behaviour will occur when Shift-dragging a read-only file and should be disabled.