We recently got a new manager at my job and he keeps on scheduling outside of my availability, which I have told him is strict and limited, and which is also in the computer that he uses to schedule. I am wondering if anybody knows if this is legal? My husband says he needs written permission from me saying I can work outside of my availability before he can schedule me that way.... If anybody knows anything, please reply. Thanks. :)

Your husband is incorrect. The employer does not need your permission to schedule you. Although, it does seem rather petty that your manager would not work with you when possible, but there is no violation of the law if he chooses not to.