Remember you also have to have mirrors.
I seem to remember it was something about if the doors were sold as an option, and wranglers for the longest time if you looked at the original window sticker did have doors listed as an option.
As far as the lip, I don't know why you wouldn't want something like that on the road, your cell phone drops out of your pocket bounces on the floor then out the vehicle breaking the window of the car next to you...
In my bronco I never considered taking the doors off, anything on that floor would roll out when you opened the door.
I think this is one of those things that that they could ticket you for but unless they had another reason to pull you over they won't hassle you.
nathan
99 xj
keeping my doors, my a/c kicks ass.