An authorized card user is someone a cardholder gives permission to use the card through the card provider. If the cardholder dies, the more important concern is whether you should continue to use the card, not if you can. You could face dire consequences in some states if you continue to use a deceased cardholder's account as an authorized user.
Each state has its own laws and approach for dealing with this situation. In general, a deceased person's debts are viewed as an obligation of his estate, not his family. Thus, if you don't use the card you are generally off the hook for balances. If you do use the card, the best-case scenario is often that the provider comes after you for the entire balance. In some cases states will prosecute users who use a deceased person's cards for fraud.
Neil Kokemuller has been an active business, finance and education writer and content media website developer since 2007. He has been a college marketing professor since 2004. Kokemuller has additional professional experience in marketing, retail and small business. He holds a Master of Business Administration from Iowa State University.