To be fair there's an extra level of complexity where the merchant has an agreement with the credit card company, listing where chargebacks are and aren't acceptable. The person organizing the match is bound to this merchant agreement, even where contracts you make with the cardbearer might contradict it.
For example if my merchant agreement with the CC company says "cardbearer may chargeback in instances where the product/service is not received or is significantly different from described", nothing I try and bind the cardholder to in terms of agreeing to no refunds will fly. I could say 'but you said you were fine with no refunds' and the CC company will say 'you agreed to give refunds under these conditions'. I speak as a merchant who sells nonrefundable deposits and wins chargebacks.
So in winning the chargeback what he did may have been "legal", you can only argue about whether or not it was morally correct.