It depends on the interaction type -- if this is a customer signup page or something, that is a very frustrating interaction. "But I don't want English, why can't I unclick it" is very annoying. For persistent interactions with a system this is probably fine.
Strictly superior here is the default in the article -- allow them to unselect, but disable the "continue" button.
Strictly superior here is the default in the article -- allow them to unselect, but disable the "continue" button.