Illinois sheriff sergeant took possession of my girlfriend's knife (the non-folding one with a 6" blade) when he put us in the back of the patrol car for a ride to the bus stn., where he returned it to her.
I think it could be confiscated as illegal, but her plan is to argue the need for it as a young female hitchhiking (sometimes) alone.
The douchebag state trooper in Nebraska kicked us off the hitchin' spot without any mention of it, though he surely saw it w/ her bag.
So maybe it is legal if unconcealed, if displayed - 'course, displaying a gun isn't legal, can't just walk into a supermarket with a shotgun in your hands.