In the New Yorker, "Judging Humor" describes the complexities of litigating humor:
In adjudicating disputes about humor, courts often must decide whether a particular communication is, indeed, funny. The cases are diverse, based on theories ranging from contract, trademark infringement, and sexual harassment to defamation.
A remarkable trend appears in these cases: they tend to track wisdom about humor developed by decades, even centuries, of humor scholars. Humor scholars have toiled to find the essence of humor, the quality that transforms a communication into something that inspires laughter. Most scholars agree that incongruity is a necessary (though not sufficient) part of all comedy. The unlikely juxtaposition of two parts of life, it turns out, gives the spark that creates a joke. Of course, the conditions must be right for the spark to work: timing, context, and the like.