Divulging information! Now that'll stop 'em.
After Macreedy realizes that Smith and the others plan to murder him as soon as it is nightfall, he decides to send a wire to the State Police. Later, when it becomes clear that Mr. Hastings never sent the wire, but gave it to Smith instead, Macreedy acts as if he has them over a barrel, because Hastings is guilty of “divulging information,” a federal offense.
What did he think, that Smith and his gang would realize they were caught and give themselves up to the police, hoping for leniency? Or, to put it differently, did it not occur to him that once he was dead, no one would know about Mr. Hastings’ minor infraction of the law?