The Supreme Court heard a group of appeals on Monday that included convicted press baron Conrad Black, convicted Enron CEO Jeffrey Skilling, and Bruce Weyrauch, an Alaskan legislator facing a corruption charge. The cases have united a broad coalition against the Justice Department: the U.S. Chamber of Commerce joins hands with the National Association of Criminal Defense Lawyers, for instance. Although the cases raise fundamental questions about the fairness and judgment of Justice Department prosecutors, they are likely to be resolved on a highly technical question: is the honest services fraud statute unconstitutionally vague? Congress adopted the statute in 1988 to reverse a Supreme Court decision that insisted on a very narrow reading of the fraud statute. The new language, codified at 18 U.S.C. § 1346, is simple: “the term ‘scheme or artifice to defraud’ includes a scheme or artifice to deprive another of the intangible right of honest services.”

Normally the Supreme Court is extremely reluctant to hold that a statute is too vague to be enforced. The test is whether a person of normal intelligence can understand and apply it. The Justice Department rose valiantly to the statute’s defense at oral argument, insisting that the language was plain and easily understood and applied. But things didn’t go well for the government on Monday. Justice Antonin Scalia, who has now repeatedly gone out of his way to express his contempt for the statute and the way it has been enforced by the Justice Department, came on like a freight train. He called the statute legal “mush” and attacked the interpretations that the Justice Department put on it, saying the Justice Department didn’t understand the law and “I don’t know how you expect the average citizen to.” Justice Breyer suggested that, as the Justice Department has construed the statute, fully “140 out of 150 million” people in the American workforce would be criminals. Justice Kennedy called the statute “a problem.” No sympathetic voices were heard for the Justice Department.

While argument focused on questions of statutory interpretation, it was also a frank expression of no confidence in the Justice Department’s management of public-integrity cases. Federal prosecutors have a solid record of bringing home convictions in such cases. But courts have increasingly expressed displeasure and occasionally anger that the cases were brought in the first place. The Seventh Circuit took the extraordinary step of ordering the release of a convicted Wisconsin public official at oral argument, adding that the government’s case may have gotten a conviction, but it never should have been allowed to go to trial. Prosecutions in Pittsburgh and Maine were also thrown out of court. And the Public Integrity Section’s highest profile case, the prosecution of Senator Ted Stevens, disintegrated after serious misconduct by prosecutors was revealed. What rang through the oral argument in the Supreme Court was an unmistakable concern that federal prosecutors handling public-integrity cases were spinning out of control.

While the Supreme Court reviewed a series of cases joined together, their ruling may affect dozens more. Alabama Governor Don E. Siegelman is the most prominent target of a federal honest services fraud prosecution so far, and the prosecution of his case remains under a cloud of accusations now raised by attorneys general across the United States, of gross misconduct by the Justice Department. Mississippi’s Paul Minor, and Georgia’s Charles Walker are other cases in which Justice Department lawyers achieved honest services fraud convictions that are now under attack.

If the Court rules as oral argument suggests they will, their ruling is likely to have far-reaching consequences for the Justice Department as well. It will have to undertake a review of dozens of cases in which convictions were secured under the statute, and it will likely have to abandon a large number of those convictions. Patrick Fitzgerald, the U.S. Attorney in Chicago, signaled his understanding of the dilemma by rushing to revise his indictment of former Illinois Governor Rod Blagojevich as the Court took up the issue.

The case comes at a particularly difficult time for the Justice Department. Leading figures in the Public Integrity Section, which handles honest services fraud cases, are now themselves the target of a criminal probe initiated by Judge Emmet Sullivan based on his determination that they engaged in serious misconduct in the Stevens trial. The section’s head, William M. Welch II, was forced to resign in October.