Univeristy of Michigan has a card they hand out for special access. It says on it "Providing immediate access to a toilet for this person is required of all businesses in Michigan by state law, per HB 5046, December 31, 2008"
https://www.legislature.mi.gov/(S(clre21q2ujqlpklajcc51ylm))/mileg.aspx?page=getObject&objectname=2007-HB-5046