Late to the party, so to speak, but for anyone checking the forums for this still, there is now an addon that unbinds keybindings for law-breaking necromancer skills. It's not perfect, of course (as it unbinds those keybinds for both front- and backbar, and doesn't discriminate between 'peaceful' areas like cities or villages and all other overland content), but it's an alternative to consider.
Lawful Necromancy
Edit: Oh, and one that works even better.
NoAccidentalStealing (+no accidental casting)
"This addon can also block you from casting criminal necromancer abilities while out of combat. To cast criminal abilities while out of combat you must hold the key for a certain duration (the duration can be set in the addon's settings)."