EDIT: Looking through my copy of Fool Moon, the only line in reference to this is "They're immune to poison and to any kind of sorcery that goes for their brain." That's...awfully thin to base a complete immunity to mental powers of all sorts on.
It's not a lot to go on, but it is enough to include in some fashion, and there's enough context and other information that we can make some reasonable assumptions as to the details. (also note that I did not suggest 'complete immunity to mental powers of all sorts'; what Bob conveys is actually more potent, if, strictly read, more narrow than my suggestion)
For instance, that particular resistance is mentioned seperately from the Loup Garou's general resistance to physical injury, so we can reasonable assume that it is, in fact, seperate; that it does not merely refer to spears of force putting holes through the creature's skull as a means of dealing with it, but rather refers to mental magic.
Moreover, Harry's interactions with the Alpha's shed some light on how we should likely inerpret the term 'sorcery' in this context. Specifically, that would be 'incredibly broadly'.
These
are assumptions, but I view them as relatively safe in the absence of further information to the contrary.
In all, there are likely certain rare 'mental powers' to which such creatures should be vulnerable, as well as certain applications of a wider range of powers that should skirt the edges of their resistance, but for the vast majority of cases, the classic mental whammy should fall wholly flat when pitted against the likes of a Loup Garou.
True. Tough if the goal is 'kill the Loup Garou' avoiding the fight and coming back in the morning is a perfectly viable tactic...if potentially one with some collateral damage.
If that's the sole goal and sole contributor to the assessment of success, then 'coming back in the morning' isn't really even necessary. Just take a few hours or days and drop a satellite on the general vicinity while they're in their human form. Or hire some mortal thugs to pop off a few magazines into the guy while he's sitting on the john.
I'm sure there's a nice celestial event sometime in the next month or two that would make one of those 'cosmic vending machine' rituals available that would suffice to do the job if we've already established that we're not on a schedule, and that there are no (relevant) consequences for delays.
