Regulation E, 12 C.F.R. 205, Electronic Funds Transfers (full-text).
Regulation E was "promulgated by the Board of Governors of the Federal Reserve System to ensure consumers a minimum level of protection in disputes arising from electronic fund transfers." It applies to electronic transactions that result in a debit or a credit to a consumer asset account. Regulation E provides that credit card account holder liability is limited to $50 (if the card is reported missing within 2 days of discovery) or $500 (if the card is reported missing more than 2 days after discovery). In such cases the remaining part of the claimed loss must be covered by the bank.
Regulation E does not apply to business accounts. Therefore, banks are not required to provide reimbursement for certain losses.