Note that section 3B in the EULA explicitly grants its users the ability to transfer the physical property and "all of your rights and obligations under the License Agreement", presumably including the Authentication Key which is needed when creating a new account. What Blizzard expressly disallows is the transfer of accounts, according to Section 1E of their Terms of Use, which is not at issue here. Apparently, Blizzard is allowing each Authentication Key to be used only once, preventing anyone with a used copy of the game from creating a new account.