Where a defendant complains of an irregularity under Federal Rule 11 that does not amount to a structural error undermining the criminal proceeding’s fairness as a whole, and has not objected to that irregularity prior to sentencing, in order to obtain relief on appeal he must establish that he would not have entered his guilty plea if not for the error in advising him under Rule 11. Rule 11 outlines in detail the list of required advisements and admonishments that must be given prior to the entry of a guilty plea. Here, the court failed to advise the defendant at the time of his plea that he would not be permitted to withdraw his plea if the court did not accept the government’s sentencing recommendations, although the written plea agreement did contain this advisement. Because the defendant did not object to the failure to so advise him, even after the court found that the government’s recommended sentence was not available to the defendant and sentenced him to a longer term, the Supreme Court held that reversal was only available if the defendant could show that the error was prejudicial in that it affected his substantial rights, i.e., that in the absence of the error claimed, the result of the proceeding would have been different. In this context, that standard of prejudice requires the defendant to show that absent the error he would not have entered his plea.