United States v. Resendiz-Ponce, ___ U.S. ___ (Jan. 9, 2007) (Ninth Circuit's decision reversing respondent's conviction for illegally attempting to reenter the United States is reversed where the indictment at issue was not defective for failure to omit an element, and consequently, the Supreme Court did not need to answer the question of whether the omission of an element of a criminal offense from a federal indictment can constitute harmless error).
http://laws.lp.findlaw.com/us/000/05998.html