James Madison presciently warned “it will be of little avail to the people that the laws are made by men of their own choice if the laws be so voluminous that they cannot be read, or so incoherent that they cannot be understood.” Sadly, however, Madison’s admonishment has fallen on deaf ears when it comes to modern statutes and regulations—which in some cases are so numerous and complex that they cannot be deciphered by trained attorneys, much less the general public. Federal prosecutors have seized the opportunity to use these vague statutes, and they now have the ability to prosecute almost anyone for anything. One protection against these incoherent laws and regulations, however, is that, in most criminal cases, the prosecution must prove a defendant had a certain degree of criminal intent (mens rea) to prove a violation. But in order for this protection to be effective, the courts must properly instruct the jury on the level of intent required by the statute. In United States v. Clay, the district court—as well as a panel of judges on the Eleventh Circuit Court of Appeals—failed in this respect. In 2002, the Florida legislature enacted the “80/20 Statute,” which requires certain medical providers receiving state Medicaid funds to spend 80 percent of such funds towards “the provision of behavioral health care services” or refund the difference to Florida’s Agency for Health Care Administration (AHCA). The statute, however, was ambiguous as to how the expenditures were to be calculated and did not set out any certain guidelines. Despite this ambiguity, in 2011, federal prosecutors indicted Mr. Clay and others for healthcare fraud and making false statements relating to not properly calculating and reporting their expenditures to the AHCA. The defendants were prosecuted under a federal fraud statute, which requires the government to prove that the defendants “knew” the reports were false. The judge, however, instructed the jury that it could convict ifthe defendants knew either that the submissions were “untrue” orif they acted “with deliberate indifference as to the truth,” which is certainly not the same as the “knowledge” required by the statute. The district court allowed this jury instruction despite a 2011 Supreme Court case that held “deliberate indifference” cannot substitute for a statutory knowledge requirement, and a three‐judge panel in the Eleventh Circuit upheld the district court’s instruction. The Cato Institute has joined with the National Association of Criminal Defense Lawyers, the Washington Legal Foundation, the Reason Foundation and twelve criminal and business law professors in requesting the full Eleventh Circuit to rehear the case and vacate the panel’s opinion. The district court’s jury instruction was a clear departure from Supreme Court precedent, and, if upheld, would weaken one of the fundamental checks on vague statutes and over‐zealous prosecutors—the requirement that the government prove someone knows they are committing a crime.