Fair Credit Billing Act
The 1974 US law that gave credit cardholders the right to dispute a charge, and with it the legal root of the chargeback.
It was an amendment to the Truth in Lending Act of 1968 and covers credit cards and other revolving credit, not debit. The cardholder has 60 days from the statement to dispute an error in writing: a wrong amount, goods that never arrived, a charge they don't recognise. The issuer must acknowledge within 30 days and resolve it within two billing cycles, and may not try to collect the disputed amount while it does.
To honour that, issuers needed a way to push the money back onto the merchant, and that became the card networks' chargeback rules. The long-standing American advice to shop online with a credit card rather than a debit card owes a lot to this statute and nothing to technology.