>Today the U.S. Supreme Court struck down a federal criminal statute on the grounds that its language is so imprecise that it violates the Constitution.
A bit moar sauce to save a click. From https://reason.com/2019/06/24/kavanaugh-accuses-gorsuch-of-judicial-activism-in-criminal-justice-case/
The case is United States v. Davis. At issue is a federal statute which, in the Court's words, "threatens long prison sentences for anyone who uses a firearm in connection with certain other federal crimes. But which other federal crimes?" That is where the debate over vagueness comes in. The law itself calls for enhanced sentencing in cases involving felonies "that by [their] nature, involv[e] a substantial risk that physical force against the person or property of another may be used in the course of committing the offense."
And what exactly does that mean? Opinions differ. And therein lies the problem. As Justice Gorsuch pointed out in his majority opinion, "even the government admits that this language, read in the way nearly everyone (including the government) has long understood it, provides no reliable way to determine which offenses qualify as crimes of violence." And "in our constitutional order," Gorsuch observed, "a vague law is no law at all" because it violates the core constitutional requirement that all federal statutes "give ordinary people fair warning about what the law demands of them."
—
In American constitutional law, a statute is void for vagueness and unenforceable if it is too vague for the average citizen to understand or if a term cannot be strictly defined and is not defined anywhere in such law, thus violating the vagueness doctrine. There are several reasons a statute may be considered vague; in general, a statute might be called void for vagueness reasons when an average citizen cannot generally determine what persons are regulated, what conduct is prohibited, or what punishment may be imposed. For example, criminal laws which do not state explicitly and definitely what conduct is punishable are void for vagueness. A statute is also void for vagueness if a legislature's delegation of authority to judges and/or administrators is so extensive that it would lead to arbitrary prosecutions.[1] Related to the "void for vagueness" concept is the "unconstitutional vagueness" concept (see below).
https://en.wikipedia.org/wiki/Vagueness_doctrine