Another, albeit rarely applicable, defense to a charge of mail or wire fraud is the defense of preemption. This is to claim that the possibility of bringing a charge under the mail and wire fraud statutes has been preempted by more recent and narrowly tailored legislation dealing with the subject of the case. As we noted earlier, for the most part, the mail and wire fraud statutes are not preempted by narrower subsequent legislation. However, a few exceptions exist.
For example, in order to charge mail or wire fraud in a tax prosecution, the federal prosecutor must contact the Department of Revenue. Most likely they will instruct the prosecutor to bring charges under the Internal Revenue Code, unless some individual was victimized by the fraud.
A more concrete exception exists with respect to the National Labor Relations Act (NLRA). Congress explicitly stated that a scheme to deprive employees of their rights under the NLRA may not be charged under the mail or wire fraud statutes. Absent such specific exceptions, however, courts will find that the mail and wire fraud statutes are not preempted by narrower legislation.