Everyone knows that with its limited resources, the Securities and Exchange Commission cannot hope to catch everyone who engages in insider trading. Still, the agency does try to be as visible and smart in this area as it can be; publicity is its favorite weapon. As Enforcement Director Robert Khuzami emphasized in a speech last year, the SEC seeks to focus its resources on cases that send an “outsized message of deterrence.”

Occasionally that message gets lost or at least muddled, but the SEC often succeeds at putting the hazards of insider trading in front of the ...