I think Stefan is write about this:
IIRC, the reason why I used `setq' is that most pre-existing global minor
modes used setq rather than setq-default. I assumed the reason was to make
it possible to make the mode buffer-local in a specific buffer.
_
> In CUA, I have this:
> (define-minor-mode cua-mode
> "..."
> :global t
> ...)
> Now, assume I have a buffer `xyz' which definitely don't want
> cua-mode enabled.
> If I do things in the following sequence, it works alright:
> M-x cua-mode RET
> C-x b xyz RET
> M-: (set (make-local-vari
