There are no laws prohibiting affection.
It would not become illegal unless it became obscene, indecent, immoral, or lewd and lascivious.
Here is the Michigan Penal Code if you want to look into it further:
http://www.legislature.mi.gov/(S(spl5c545im5ii5viyc3fxc45))/mileg.aspx?page=getObject&objectName=mcl-328-1931-XLVIII&highlight=penal%20AND%20code