Rep. Mark Souder (R-Indiana), perhaps the most fanatic opponent of sensible marijuana laws in the U.S. Congress, announced that he is resigning this morning amid revelations that he had an affair with a 45-year-old staffer. Souder, who was preparing to run for his ninth term in office, has spent the last 16 years fighting for cruel and unscientific drug policies, many of which have caused irreparable harm to his country and his constituents. Among the lowlights: In defiance of mountains of evidence…