This circumstance was recently featured in the NYT. The article is of note in this blog mostly because it quotes a well-known Michigan divorce attorney; Richard Roane of Grand Rapids.
With New York finally following the rest of the states in 2009, all 50-states now have "no fault" divorce laws on the books. Each state is different, however, as to how adultery, if and when proven, is factored into the divorce judgment.
The Michigan Penal Code has long-contained a chapter on adultery, defined as, "the sexual intercourse of 2 persons, either of whom is married to a third person." The scope of the criminal conduct includes divorced but cohabiting persons. The statute requires the cuckolded spouse to swear-in as the complaining witness and has a brief statute of limitation; one year.