What kind of ops?
I recently got one to use on Tyrolean traverses because the cheeks of an ordinary pulley tend to rub the rope when you go sliding out across the traverse.
The button is very well made with a stiff spring. It has to be depressed completely below the inner surface of the cheek plate before the plate can rotate open. It takes two simultaneous forces at right angles to get the cheek plate to open: depression of the button and twisting of the plate with respect to the rest of the pulley in the correct direction. Easy to do with two hands, possible to do with just one hand using the thumb on the button.
Could it happen by accident? Let me answer this way: if you intentionally set out to rig up a scenario in a real tree in which you were able to open it without touching it, you deserve an engineering award and I would love to have a picture of your rig to hang on my wall!! But I suppose it is possible.
