Allow me to simply point to the Blizzard EULA, which is applied to EVERYTHING Blizzard, even just installing Battle.net, before you ever even purchase something from them.
I’ve bolded the more important bits.
Specifically the section on Alterations to the EULA, and Termination of the Agreement between Blizzard and yourself.
Alterations to the Platform.
Blizzard may change, modify, suspend, or discontinue any aspect of the Platform or Accounts at any time, including removing items, or revising the effectiveness of items in an effort to balance a Game. Blizzard may also impose limits on certain features or restrict your access to parts or all of the Platform or Accounts without notice or liability.
Termination:
Blizzard reserves the right to terminate this Agreement at any time for any reason, or for no reason, with or without notice to you. For purposes of explanation and not limitation, most Account suspensions and terminations are the result of violations of this Agreement.
In the event of a termination of this Agreement, any right you may have had to any pre-purchased Game access or virtual goods, such as digital cards, currency, weapons, armor, wearable items, skins, sprays, pets, mounts, etc., are forfeit, and you agree and acknowledge that you are not entitled to any refund for any amounts which were pre-paid on your Account prior to any termination of this Agreement. In addition, you will not be able to use the Platform.
TL:DR : They can change the EULA you agree to at anytime, and if you don’t uninstall the products and stop using the platform, you automatically agree to the new updated EULA.
They can restrict your access to any part of their games or platforms in part or in whole at any time with no liability to themselves for doing so.
Finally, they can terminate your agreement ( read Account ) with them at any time, for any reason, or NO REASON.
This has been in place since Battle.net was a thing, ( read A LONG TIME AGO ) They have never had need to spell out any rules or regulations, nor give specifics reasons that would lead to punishments. They have been able to enforce any punishment they feel like, at any time, for any reason, since the dawn of Battle.net.