First, to address the use of the digital property that is owned by WotC (the cards): What you are buying and selling are licenses to use WotC's property. This is done all the time in the software world. Namely, WotC owns the cards but sells you the right to use them but they are positioned to revoke those licenses. What you posted regarding use and ownership is very incomplete.

WoC doesn't have to use the word revokable, Im sure their attorneys are more than capable to write an online contract regarding the use of their services that allows them to ban a user for what they view as a violation of their ToS.

The chargebacks are likely going to be a problem for your friend. He made use of those ToS, digital cards, their licenses and the online services provided by WotC so he owes monies for those licenses, their use and the online services. By filing for chargebacks he's opened himself for legal action by WotC. They have unlimited resources to be made whole.

On the whole I'd say your friend made some, shall we say, questionable decisions.