For a box to only open in zero G, you could have weighted pins in all 6 directions, pulled back by very weak springs. In normal gravity, whichever pin(s) are "d

For a box to only open in zero G, you could have weighted pins in all 6 directions, pulled back by very weak springs. In normal gravity, whichever pin(s) are "down" will extend and lock it. It would have to be in very low gravity for enough time for the pins to retract to unlock.