Well, you still gots to be careful. There are brandishing and affray laws on the books that make it unlawful to use just about anything short of a limp noodle to intimidate others. The rotten part is who defines the intimidation, and when someone who doesn't think the way you do goes whining to the nearest LEO that you "threatened" them with your knife by opening it and brandishing it in public, well, you can get the idea how this goes down. You might not get arrested, the LEO might not take the knife from you, but you will at least have to present him with it, deal with the hassle, do some explaining, and likely get a warning that marks you in his memory the next time he might see you. I know, it ain't right, but this is the reality of the world we live in, and the sad fact is those who don't want to control more and more those that do (fill in the blank). Such thinking is what has led us to these wonderful zero tolerance policies that our kids are stuck dealing with.

Legal length or not, you just can't walk around with an open knife of any size in your hand these days and not expect to have problems. I don't care about getting "the look", but I don't like it when the LEO has to come talk to me about it, and I don't really think they appreciate it much either.