Setting: Present-Day USA
I'm writing a Batman fanfiction that's become a bit epic in scope. (I'm on the third installment in an AU.) Some quick background: in this AU, Batman was arrested, unmasked, packed off to Arkham and spent two years there before being released. There are other details that make his remaining in custody plausible, but they're not germane to the task at hand.
Currently, he's been remanded to the Gotham City Mental Health Dept. as an outpatient and it's been made clear that if he's caught engaging in any vigilante activity, he will be returned to inpatient status.
So. Suppose a scenario were to arise where the police need his help? I realize that it would be irregular, but is there any strictly legal reason why the police commissioner couldn't deputize him for the duration of the emergency?
At the end of the day, I know that DC canon involves a certain amount of handwaving, and if I have to, I can do the same. I'm just trying to figure out the rules before I start breaking them.