this is also new info to me....i live in west minneapolis, and go to school in st.cloud,MN....
I've personally asked multiple cops what exactly the legal length is to conceal and carry a knife.....and none of them could give me an answer! most cops dont even know in my experience.....but they did tell me (after I showed them my knife) that whatever you're carrying is usually just fine....as long as its not some pocket sword or a switchblade, it doesnt matter to them until it ends up stuck inside someone!
I carry a gerber harsey air ranger, or a large griptilian in blaze orange....police officers have looked at both when i ask this question (or they had a different reason to talk to me haha) and have never had a problem with either.....
in other words....ive never been able to find a straight answer to what the legal length is....just use common sense....
unless you plan on using it for self defense, then it shouldnt be a big deal....hope that helps....