The United States Supreme Court held in the 50s that abetting only applies to substantive counts, not to conspiracy counts. Pereira v. United States, 347 U.S. 1 (1954). The Fifth Circuit noted that:
In Pereira the Court, in affirming one defendant’s conviction for conspiring to commit mail fraud and aiding and abetting the commission of mail fraud, rejected the double jeopardy plea. Petitioners had alleged that their conviction on both the substantive counts and a conspiracy to commit the crimes charged in the substantive counts constituted double jeopardy. ‘The Court found that: The essence of the conspiracy charge is an agreement to use the mails to defraud and/or to transport in interstate commerce property known to have been obtained by fraud…Brading’s conviction does not turn on the agreement. Aiding, abetting, and counseling are not terms which presuppose the existence of an agreement. Those terms have a broader application, making the defendant a principal when he consciously shares in a criminal act, regardless of the existence of a conspiracy.’
See United States v. Cowart, 595 F.2d 1023 (5th Cir. 1979)