No, you don't. However it this background check is related to a pre-employment application you probably won't get hired. And that is completely legal. If this check is part of a periodic update for a job that you already have, you may well be terminated for refusaing to sign an authorization. And this too is perfectly permissible. With at will employment (and most work relationships are) an employer can hire/fire an employee for just about any reason it sees fit. At least if there is no prohibition against this by virtue of a union/employment contract, company policy or some form of actionable discrimination.