In the UK version, the digital product may become unusable, in the US version, the device may become unusable:

The agreement for UK accounts now states digital products are “licensed only for personal and non-commercial use”, and that any “unauthorised use of a Digital Product may result in the Digital Product becoming unusable”.

This differs slightly from the US, which states: “You acknowledge that if you fail to comply with the foregoing restrictions Nintendo may render the Nintendo Account Services and/or the applicable Nintendo device permanently unusable in whole or in part.”