For a glimpse into the treacherous territory of sexual relationships on college campuses, consider the case of Caleb Warner.

On Jan. 27, 2010, Mr. Warner learned he was accused of sexual assault by another student at the University of North Dakota. Mr. Warner insisted that the episode, which occurred the month prior, was entirely consensual. No matter to the university: He was charged with violating the student code and suspended for three years. Three months later, state police lodged criminal charges against his accuser...