Regulation E prevents you from charging a fee for an overdraft resulting from an ATM or one-time debit card transaction unless you have complied with the prescribed procedures for obtaining the consumer's opt-in for overdraft services for such transactions, and the consumer has provided an opt-in.
The Bureau considers the charging of an OD fee on an ATM or one-time debit card transaction potentially unfair if it was authorized against a positive balance regardless of whether the consumer has opted in under section 1005.17. On the other hand, if the transaction was authorized against a negative balance because the consumer has opted in under 1005.17, I don't think the CFPB's Circular would apply.