But the lengthy Alaska rules that described the ethical duties of state legislators did not require Weyhrauch to disclose such potential conflicts. Disclosure rules are prophylactic rather than substantive in nature, and Alaska’s omission of this duty in the context of rules that required disclosure in other situations suggests that the state made a deliberate policy choice not to require disclosure in these circumstances. Weyhrauch was not accused of actually selling favors, but only of violating a pro forma disclosure requirement that Alaska had specifically declined to impose.The trial judge initially concluded that Weyhrauch could not have committed honest services fraud because he had done everything that the state of Alaska asked of him. The 9th Circuit reversed that decision, however, stating that the vague federal law protecting the “intangible right to honest services” imposed additional, undefined duties on state lawmakers — and by extension, private employees — over and above the expectations of those to whom the “honest services” are actually owed.The honest services provision is so vague that it mocks the principle that citizens should know in advance what the law is. Unless the Supreme Court reverses Weyhrauch’s conviction, neither lawmakers nor employees can assure themselves that they are providing “honest services” simply by scrupulously meeting all job requirements. Instead, they must guess what additional requirements federal prosecutors and courts may impose after the fact.Nor are vague offenses like mail and wire fraud the only federal crimes that ordinary Americans inadvertently commit. Traditionally, a reasonable mistake about the facts is a defense to a criminal charge, but many modern federal criminal laws lack any language limiting their reach to those who commit harmful acts with mens rea, or a “guilty mind.” As a result, unlucky individuals can be convicted under federal law — and even sentenced to prison — for reasonable mistakes.Moreover, federal criminal laws increasingly punish those who violate the Code of Federal Regulations, a vast web of ever-changing regulatory requirements promulgated by bureaucrats. Even experts often disagree about what these regulations mean. But following the advice of such an expert in good faith is no defense for those unlucky enough to be criminally charged for misunderstanding the code.The Supreme Court has tolerated these and other excesses in the federal criminal law for too long, and the Black and Weyhrauch cases offer it a good opportunity to begin the long process of restoring important traditional limits on the reach of the criminal law.Marie Gryphon is a senior fellow at the Manhattan Institute’s Center for Legal Policy. Her new paper, “It’s a Crime? Flaws in Federal Statutes that Punish Standard Business Practice,” was released Dec. 9.