I believe butterfly/balisong knives are considered "gravity" knives, and therefore under Michigan law are illegal.
EDIT: Keep in mind, there is a part of the Michigan knife law that reads the listed knives are considered illegal if used in conjunction with a crime...or some such legal gibberish. Would you get hassled by a police officer? Probably. Don't go around flipping it and you probably won't have an issue. Butterfly/balisong knives are very nice in that they are almost lock-failure proof since you're holding onto the folding handles. Benchmade's 51, 53, and 32 would make good general purpose/utility knives.