He can say it but do you really think we would have let it happen? Seriously? The all powerful U.K.
If it happened (and remember, he's not a politician in power at the moment, though he may become one; it's just his party's vision, not official EU policy - yet) then seriously, yes. We'd be out like a shot; I don't believe that that many remainers would be in favour of a U.S.E - I'm just staggered that so many seem content to stick their fingers in their ears and go 'La, la, la - it wouldn't happen to us.' Fortunately, we're leaving anyway, so it's a hypothetical question.