When can landlords keep you deposit in NC?

My friend moved out of her apartment and they're keeping her whole deposit. They gave her a lost and said they're using $1000 for the walls (thumbtack holes, oily residue from sticky tack and paint) which is outrageous. Don't they have to show receipts of what they paid for? Also is a cleaning fee something that they can use a deposot for? Where can I find they laws for North Carolina?