IANAL but, If I’m understanding this article right, it sounds like their new terms are going to give them the authority to brick your Nintendo console if you reverse engineer it. If this is the case I firmly expect this is going to be challenged in court because if I understand the current laws right this directly contradicts the end users right to reverse engineer Hardware that they own. Nintendo would be allowed to terminate your account and block access to the network with them over it as that’s something that they actively maintain, however I don’t believe they can legally remove access to a piece of Hardware that you purchased, soley due to the fact that you reverse engineered and installed a third-party software to it.

Now don’t get me wrong, they can definitely refuse warranty if(and only if) that modification caused a malfunction, however it’s a big jump to go from we’re not going to repair your device and you’re no longer allowed to access our Network to this $400 object that you purchased is now a brick.