Green’s Dictionary of Slang

(US) a right turn followed by a U-turn (or a U-turn followed by a right turn) depending on the situation.

2000		Battle Creek Enquirer (MI) 24 Aug. 3/5: These are known as indirect left turns or a ‘Michigan left’.
2017		S.M. Jones August Snow [ebook] I threw O’Donnell’s driver a curve by making a quick ‘Michigan left’.