Suppose your city awards a lucrative contract for the purchase of new garbage trucks. Afterward, the company that won the bidding offers your mayor a gift of $13,000. The mayor never asked for a penny; but he’s offered the money and he takes it. Has the mayor committed a crime?

You might think the answer is obvious, but evidently it isn’t—at least under the federal statute prohibiting “theft or bribery” in programs that receive federal funds. Or so the Supreme Court has just decreed, ruling in favor of the former mayor of Portagee, Indiana, who was convicted under just those facts. And if the outcome seems peculiar as matter of policy, it is defensible and even correct as a matter of democratic principle—the principle here being that when a legislature chooses to make an act a crime, it should specify as tightly as possible what is being forbidden.

James Snyder, the mayor in question, challenged his conviction on the ground that Section 666 of Title 18 of the federal criminal law forbids only bribes (with the implicit quid pro quo) and not gratuities (a gift given after a decision has been made). The federal appellate courts had split on the question. The Supreme Court, in a 6-3 decision, ruled that Synder is right, meaning that although he might have broken state or local law by accepting the $13,000, he did not violate federal law.

Justice Brett Kavanaugh’s majority opinion rests largely on interpretation of the legislative history behind Section 666, an interpretation the dissent sharply disputes and which I will not recapitulate here. But I will mention that Kavanaugh scores a nice point when he notes that if we read the statute to bar gratuities, a word its text does not include, we face an anomaly: The federal statute barring federal officials from accepting gratuities authorizes a maximum sentence of two years in prison, while under the government’s reading of Section 666, a local official who does the same thing could face up to 10. Yikes! And although lots of states forbid both bribes and gratuities, these rules, like the statute covering federal officials, treat accepting a gratuity as a much less serious offense than accepting a bribe. It would be strange for Congress, in a statute that does not mention gratuities, to treat both offenses with equal harshness.

Fair enough. But Congress does some funny things, and not all of them are humorous.

Which is why what matters most is the majority’s conclusion that to read Section 666 as barring gratuities would deny “fair notice” of what was forbidden. The only criterion the government offered, Kavanaugh writes, is that gratuities violate the law only if they’re wrongful.

This, he correctly concludes, is no guidance at all: “What about a $200 Nike gift card for a county commissioner who voted to fund new school athletic facilities? Could students [at a state university] take their college professor out to Chipotle for an end-of-term celebration? And if so, would it somehow become criminal to take the professor for a steak dinner?”

Kavanaugh goes on: “The Government’s so-called guidance would leave state and local officials entirely at sea to guess about what gifts they are allowed to accept under federal law, with the threat of up to 10 years in federal prison if they happen to guess wrong. That is not how federal criminal law works.”

The majority also rejects the government’s argument that prosecutors can be trusted not to prosecute “small-time” cases: “As this Court has said time and again, the Court ‘cannot construe a criminal statute on the assumption that the Government will use it responsibly.’”

As Justice Neil Gorsuch notes in his concurrence, when there’s doubt about whether a criminal statute covers the conduct, the court must issue a judgment “not for the prosecutor but for the presumptively free individual.” That’s how freedom works.

Justice Jackson’s dissent, joined by Justices Sotomayor and Kagan, looks mainly at statutory language and legislative history, but also seeks to address the issue of fair notice head on. She argues that whatever the limits might be on what constitutes a wrongful gratuity, Snyder’s would plainly fall on the criminal side of the line. Thus the other examples the majority raises — “fretting,” in Jackson’s nicely chosen word — can be left for another day.

I think Jackson is right that it’s hard to see how Snyder could think that if he could accept a dinner or a pair of sneakers he could take a $13,000 check. Yet I still think Kavanaugh has the better of the argument.

Courts should not draw vague lines around criminal law. That which is forbidden by the state should always be crystal clear. Particularly in an era so heavily regulated, we mustn’t leave it up to individuals to guess whether they’re committing a crime.

I quite understand the practical difficulties created by the court’s conclusion. What will some other mayor do, when faced with a choice between the company that paid Snyder a generous gratuity—now blessed by the nation’s highest court—and some rival company whose intentions he might not know? Although most public officials are surely too honest to be influenced, there exist some who will be more likely to choose the company they think will give them a gift.

At which point, the race to the bottom begins.

So what Snyder did was terrible. But a court is not free to deem an act criminal simply because the act is egregious. Rather, it is up to the legislature to ban the conduct, using clear and precise language. Your move, Congress.

Stephen L. Carter is a Bloomberg Opinion columnist, a professor of law at Yale University and author of Invisible: The Story of the Black Woman Lawyer Who Took Down America’s Most Powerful Mobster.

This article was provided by Bloomberg News.