MasterCardの規則及び規制 (PDF) (pdf)
5.8 Merchant Obligations for Acceptance
An Acquirer must ensure that each of its Merchants complies with the Card acceptance requirements set forth in this Rule with respect to the Acceptance Marks specified in the Merchant Agreement.
5.8.1 Honor All Cards
A Merchant must honor all valid Cards without discrimination when properly presented for payment. A Merchant must maintain a policy that does not discriminate among customers seeking to make purchases with a Card.
A Merchant that does not deal with the public at large (for example, a private club) is considered to comply with this Rule if it honors all valid and properly presented Cards of Cardholders that have purchasing privileges with the Merchant.
Visaの規則及び規制 (PDF) (pdf)
188.8.131.52 Honoring All Visa Cards
Visa Merchants may not refuse to accept a Visa product that is properly presented for payment, for example, on the basis that the Card is foreign-issued, or co-branded with the Merchant's competitor's Mark. Merchants may attempt to steer customers who initially present a Visa Card to an alternative method of payment, such as by providing discounts for cash, but may not do so in a confusing manner that denies consumer choice. Merchants may also consider whether present circumstances create undue risk, for example if the sale involves high-value electronics, but the Card signature panel is not signed, and the Cardholder does not have any other identification.