Legal Question in Employment Law in California

Re: Can my ex-employer?

Without more information it is impossible to answer your question. If you were arrested for stealing money from your employer, then yes, the employer can offset its loss against your paycheck. If the loss was inadvertent, or a mistake, then probably not. If the arrest is completely unrelated to work, the employer has no basis to hold your pay and should, at least, mail the check to your home, if you are unable to pick it up.