I haven't come across the option you've mentioned yet in the Ruleset Reference, if it is there I've also missed it.
Completely stopping an item from being used may be difficult(Or impossible) via scripting but perhaps you could figure out something using "BattleUnit.isKneeled" and "BattleUnit.isStanding".
If these actions can be performed via scripting you may be able to make it look like the item was never used:
. Silence the sound FX. (Either prevent it or swap it to a sound effect that has no audio in it.)
. Refund the TU cost of using the equipment.
. Replace the Hit animation & projectile sprite with a blank image.
. Increase bulletSpeed, explosionSpeed to as close to instant as possible.
. Temporarily toggle followProjectiles: to FALSE.
. display a message with either "flashMessage" or "flashLongMessage" that says "Cannot be used while standing."
I'm not sure if all of the above can be done currently though.