Judge Posner, the author of Sex and Reason, had occasion to reflect on the meaning of the term “sexual activity” in 18 U.S.C. 2422 (the statute does not define the term) in this opinion.

We need to decide whether “sexual activity” encompasses a broader range of acts than “sexual act.” If it did, one would expect the term to be defined in the statute, to indicate just how broad that range was. Is watching a pornographic movie, or a pole dancer, or a striptease artist, or Balthus’s erotic paintings, or Aubrey Beardsley’s pornographic sketches, or Titian’s “Rape of Europa,” or “Last Tango in Paris” a “sexual activity”? How about inducing someone to watch one of these shows?

Judge Posner has a lengthy discussion about whether masturbation is a “sexual activity.” Will I go blind reading this passage?

Last the government cites cases in which courts have referred to masturbation as a form of sexual activity. In none was the question that this appeal presents raised. . . . In our case of United States v. Cochran, 534 F.3d 631, 634 n. 3 (7th Cir. 2008)—another case factually similar to the present one—the question of the meaning of the term “sexual activity” in section 2422(b) was neither raised by the appellant nor answered by the court. Finally, United States v. Womack, 509 F.2d 368, 372 n. 4 (D.C. Cir. 1972), was a pornography case; it had nothing to do with section 2422(b), and merely illustrates (as do the other cases cited by the government) that masturbation is a form of “sexual activity” in the ordinary-language sense of the term, which judges use on occasion just as laypersons do. Masturbation is also a “sexual act” in that sense, but not in the statutory sense.

 

Posner even quotes the Wikipedia page for “Human Sexual Activity!”

Wikipedia defines “sexual activity” very broadly; the Wikipedia entry for “Human Sexual Activity” says that “sexual activity . . . includes conduct and activities which are intended to arouse the sexual interest of another, such as strategies to find or attract partners (mating and display behavior), and personal interactions between individuals, such as flirting and foreplay.” “Human Sex- ual Activity,” http://en.wikipedia.org/wiki/Human_sexual_ activity (visited April 1, 2011).

H/T How Appealing