In recent decades, the scope of federal law has grown massively. And with that growth has come the risk that Americans will be ensnared in criminal or civil proceedings for activities they had no idea were illegal.
It is often said that ignorance of the law is no excuse, and in general that is true enough. But the government has an obligation to afford people fair notice of what the law requires or forbids. At a time when there were relatively few penal statutes on the books, most of which reflected widely held moral values, it might have made sense to expect people to understand their legal obligations without much effort. That is no longer true. As former Attorney General Edwin Meese and scholar Paul Larkin have noted, “[t]he offenses found in federal law today reach far beyond what common sense and generally accepted moral principles would forbid.”
Frequently, crimes are not even defined specifically in any statute but are instead defined in agency regulations. So, a citizen attempting to figure out his or her legal obligations would often have to dig through not only the U.S. Code but also the Code of Federal Regulations. As Justice Clarence Thomas has observed, “The number of federal laws and regulations that trigger criminal penalties may be as high as several hundred thousand.” When Justice Neil Gorsuch was a Tenth Circuit judge, he decided a case in which a federal agency “los[t] track of its own controlling regulations and applie[d] the wrong rules in order to penalize private citizens.” When rules become so numerous and complex that even the government cannot keep up with them, something has gone seriously wrong.
The rule of lenity provides one way of dealing with this problem. Under this longstanding rule, derived from English common law, ambiguities in penal laws are interpreted in the way most beneficial to the accused (and against the government). On the current Supreme Court, Justice Gorsuch has emerged as the most prominent champion of the rule of lenity, invoking it in several cases (including one decided just weeks ago). That is no surprise, for Gorsuch has elsewhere noted his concern with the startling possibility that “there is no one in the United States over the age of 18 who cannot be indicted for some federal crime.”
And as Justice Gorsuch notes, even when the Court does not explicitly invoke lenity, it still often seems to be doing some work in the background, protecting the “presumptively free individual” against dubious assertions of power. In a 2021 case, for example, Justice Amy Coney Barrett disclaimed reliance on lenity but observed that “the Government’s interpretation of the statute” should be disfavored because it “would attach criminal penalties to a breathtaking amount of commonplace computer activity.” More recently, in a case interpreting a federal obstruction-of-justice law, Chief Justice John Roberts explained that the Court has “traditionally exercised restraint in assessing the reach of a federal criminal statute,” in order to avoid “giving prosecutors broad discretion” that would usurp Congress’ role in defining crimes and penalties.
To be sure, because lenity kicks in only when a statute is ambiguous, there is disagreement over the threshold that triggers the rule (does a statute need to be “grievously ambiguous” or just “ambiguous”?). But whatever disputes might exist about the rule of lenity’s application, the basic principle is an important one.
Closely related to lenity is another doctrine that protects the value of fair notice: the void-for-vagueness doctrine. Under the Fifth Amendment’s Due Process Clause, a statute is unconstitutionally vague if it “fails to provide a person of ordinary intelligence fair notice of what is prohibited, or is so standardless that it authorizes or encourages seriously discriminatory enforcement.” In Sackett v. EPA, PLF’s landmark case about the reach of the Clean Water Act, Justice Samuel Alito’s opinion for the Court noted that “the EPA’s interpretation gives rise to serious vagueness concerns” because the agency’s “hopelessly indeterminate” definition of waters of the United States “provides little notice to landowners of their obligations.” These due process concerns reinforced the Court’s conclusion about the meaning of the law.
Finally, the mens rea canon of statutory interpretation—under which a criminal statute is presumed to require “a culpable mental state” for each element of the crime—also can help “shield people against punishment for apparently innocent activity.” Justice Brett Kavanaugh has advocated that the Court “vigorously apply (and where appropriate, extend) mens rea requirements,” in order to respect “the importance of fair notice in federal criminal law.” Although Justice Kavanaugh suggests heightened mens rea requirements as a substitute for lenity, in many ways the two can and should work in tandem.
Overbroad and overly numerous laws leave the government significant discretion that can be abused. Selective enforcement was at issue in multiple cases decided this past term by the Supreme Court, and it is a serious threat to liberty. Even if a given law or regulation is rarely enforced, the fact that it remains on the books allows the government a convenient way to target those it wishes to punish. Prosecutors can always decline to charge minor violations, thereby narrowing the effective scope of a prohibition. But they can also make the opposite choice. When Americans are left reliant on the grace of prosecutors, effectively delegating the power to define crimes to the Executive Branch, liberty is placed in jeopardy. Doctrines like the rule of lenity are crucial bulwarks against such abuses.