Originally Posted by
flarmip
Therefore I would say it is highly situation and fact dependent as to whether refusing to unnecessarily check-in hand luggage would constitute "reasonable grounds to deny ... boarding". I don't think a blanket answer can realistically be provided.
Ultimately, it would depend upon the particular scenario, but I think it would be a gutsy performance to refuse to surrender your carry on, be denied boarding and then pursue the litigation/CEDR route. If there are people willing to be turfed off a flight to make a point about hand-baggage, I'm not one of them.