AKTI is the American Knife and Tool Institute (akti.org). They are a knife rights advocacy group. Think NRA, but for knives, and less influential.
I don't know what you're talking about in regard to legally carrying a knife in a sheath. Under Michigan's state law, there is no restriction on the open or concealed carry of folding knives, regardless of whether they're carried in a sheath or pocket. Carrying a blade with length greater than 3"
with unlawful intent is illegal, but otherwise there is no length restriction. As far as fixed blades and concealment, my understanding is that MCL 750.227 is generally interpreted to apply to double-edged fixed blades, and may apply to to single edged fixed blades as well, depending on how your prosecutor is feeling. Open carry of fixed blades is permitted outside of a vehicle, in a sheath or otherwise, and concealed carry is permitted when actively engaged in hunting. Unfortunately, a CPL does not extend to concealment of knives. Of course, I'm not a lawyer, so if someone out there knows better, please say so.
If asked, NEVER tell a LEO your knife is for self-defense. Knives - even big ones - are not a great choice for self defense anyway (especially if you lack significant hand-to-hand combat training) and are at best a last ditch backup to your gun.
Obviously, this is the state law and may vary from town to town. Below is a link to various local knife laws courtesy of handgunlaw.us, but understand that it may not be all-inclusive or 100% accurate. Go to municode or individual township/city offices for a more accurate reading of the various ordinances.
http://www.handgunlaw.us/documents/USKnife.pdf