thats what i thought.. lowering improves your acctual cars ability to avoid pedestrians.. the only danger i can see with it is for one's self if you get side swiped you more likely to be rooted (expecially if its a 4wd with a lifter kit lol) the only negative i know of lowering is it reduces your turning circle, which to me isnt very dangerous at all its just inconvenient to need to do an 8 point turn...
but yes it should be ground clearance of front and rear bars.. (if you do it from lowest point cops will probs do it from your mudflaps..)
knowing WA this will take a few decades to get here