I try to use common sense when carrying weapons in my truck ... I keep my swords in a case, put long weapons in the bed of the truck (if I have more than one I tie them together). And I hope the cop has some common sense too -- if he sees my uniform and that the weapons are "traditional" he'll let it pass. I haven't been pulled over in awhile, so my theory hasn't been tested.
Of course, if the cop catches me going all Jack Nicholson on somebody's windshield with my stick, that may be hard to defend.
There is a great streak of violence in every human being. If it is not channeled and understood, it will break out in war or in madness. ~Sam Peckinpah