[RPG] Ex-wizard that pretends he still is a wizard

Switching default male pronoun to default female, in deference to Wizards’ own style and to match rules quotes.

Her wizard class features give her no special ability to activate the item

As she does not have access to Enchantment or Evocation spells, she does not qualify as having those spells on her spell list for the purposes of activating spell-completion and spell-trigger items (e.g. scrolls and wands), even for spells that are otherwise on the wizard spell list. The School Specialization sidebar makes that much, at least, quite clear:

Spells of the prohibited school or schools are not available to the wizard, and she can’t even cast such spells from scrolls or fire them from wands. (PHB1 p57)

However, Use Magic Device is all about using items you usually can’t

A wizard could use the Use Magic Device skill to activate such items, the same as any other character. Wizards don’t get Use Magic Device in-class and don’t tend to invest heavily in Charisma, but the loremaster prestige class is really easy for a wizard to enter, and would get you Use Magic Device.

Anyway, that a wizard can Use Magic Device on spell-completion and spell-trigger items is, unfortunately, not immediately clear from the rule I quoted: that rule says they are not available, with no qualifications. Unfortunately, Wizards had this tendency, particularly early on, to assume single-classed characters, and ignored cross-class skills. It probably simplified the language, but at the cost of making things confusing when you stepped away from those assumptions.

For this, I am going to draw parallels to the question of whether or not a multiclass specialist wizard may cast spells of her banned school with her other class. The books explicitly allow this (Complete Arcane 185), despite that very same rule I’ve quoted above which seems to say that the specialist wizard may not cast those spells at all. What that line actually means is that the wizard class itself does not give you the ability to cast those spells or use those items when you specialize and ban those schools. You can still use the usual methods around that inability, the same as, say, a monk could.

The best way for the wizard to defend a spellbook is the same as the best way for you to protect your precious computer files - have multiple backups.

But, if he hasn't had time to make a copy, if he knows someone is trying to steal the book back, he wouldn't leave the book in the shop overnight. He'd keep it on himself, likely guarded by as many guards as a 7th level wizard can afford to hire on a temporary basis.

If he must leave the book in the shop for plot points, he'd certainly have the book very well protected and secured. He's 7th level, so he knows 4th level spells. He might, for example, use Stone Shape to fabricate a 'doorless' safe in a wall or floor block. And he'd certainly know to keep the book in a lead box to block scrying and detection attempts. He could also use illusions to hide/conceal the book. And decoy books and safes to waste the thieves' time. And of course, a 1st level Alarm spell on the shop would work wonders. He might hire a dozen men at arms who hang out in a neighboring building waiting for the alarm to go off.

You say he can't use anything too damaging in terms of traps. Well, poison gas doesn't cause much physical damage and dissipates after a while. And while you say its illegal for him to create fatal traps, a) he may not care, b) bribes and Charm Person can get the well-to-do out of trouble, and c) dead thieves can't report you to the town guard. If you don't want to do that, you can always fill the shop with a Web.

Beyond defending his shop, since he knows there's likely going to be a break-in, he might have a familiar watch the shop from a distance and follow the thieves back to their home/inn/hideout. And when they aren't looking, he can rob them blind.