on drop:
    if {drop.%player%} is 0:
        message "&dアイテムをドロップできないよ！解除したい場合は/drop on" to player
        cancel event
command /drop <text>:
    trigger:
        if arg 1 is "on":
            delete {drop.%player%}
        else if arg 1 is "off":
            set {drop.%player%} to 0