Ghirardelli Chocolate bars and squares are NOT gluten-free.
From GlutenFree Indy, excerpt from a post on a well known chocolate bar:
Thank you for your email regarding Ghirardelli Chocolate. The 60%Bittersweet Chocolate Chips are manufactured on a line free of gluten. In June 2008, the Ghirardelli Chocolate Company introduced new milk chocolate bar which has a barley gluten as an ingredient. As a result,the line which produces our chocolate bars and squares will no longer be safe for consumers with gluten allergens. Kind regards, Shawna OrtezSenior Consumer Affairs Coordinator Ghirardelli Chocolate Company1111 - 139th AvenueSan Leandro, CA 94578