The case involved a drug "rip-off" in which the defendant and his co-conspirators agreed to sell sugar as heroin to unsuspecting buyers.

The court's opinion addressed—and eventually dispensed with—Judge Learned Hand's famous analogy in United States v. Crimmins 123 F.2d 271, 273 (2d Cir.

But agreement or conspiracy requires knowledge that there is such a red light, or that the mails will be used.

The court identified these reasons as protecting society from concerted criminal activity and the social threat posed even by an inchoate crime.

Justice Potter Stewart dissented, arguing that the structure of the assault statute and legislative history of its predecessor supported his interpretation that the statute only applied if the defendant knew his victim was a federal officer.