I had an Illinois state trooper ask what I was carrying while we were both waiting in line at the McDonalds on a toll road overpass (I-88 out by I-39). He saw the pocket clip on my beat up old green and purple 940. I thought I was in for a hassle, until he said "nice knife, but I couldn't handle the purple" and showed me the black combo-edged BM 943 he was carrying.
Another time I was with some folks in Wisconsin and one of them was stopped by a local cop, again spotted via pocket clip. He was carrying a little ~3" liner-lock of some type. The cop asked to see it and proceed to attempt to wrist flip it open. It took him, no joke, a couple of dozen tries to get it to open. He flailed around to the point that it was taking so long it was a bit embarrassing to watch him. When he finally got it to open, he declared it a "deadly gravity knife" and said that it was completely illegal and "you could be in a lot of trouble". The options he posed where these: he would confiscate the deadly weapon and give him a verbal warning, or he could take a free trip in the back of a cop car. As this was happening, I unclipped the BM 707 that was in my right front pants pocket and let it fall inside. I know that means I was concealing it, but my 707 will flip open if you just give it a stern look

so I knew it was, at least to this nutball cop-building-a-free-knife-collection also a "deadly gravity knife", ha.
I was so pissed after that encounter. The person I was with just gave up the knife, saying the fifty bucks to replace it was a better deal than trying to fix some cop's bad behavior and possibly ending up in trouble doing it. Since then I've seen a few other LEO bad behavior incidents in person that have left me with a deep and abiding distrust of law enforcement. Even if most of them are great, the fact that they protect the bad apples rather than punish them more severely than citizens (which IMO is what should happen when someone given that kind of power abuses it) is what causes my concern.
Better safe than sorry, when some badged bully can ruin your day. That's why I've recently taken to actually obeying the brain-damaged Chicago 2.5" blade length limit, after ignoring it for most of my life.