“Vague laws invite arbitrary power.”

That’s the opening line and general theme of Justice Neil Gorsuch’s concurring opinion in Sessions v. Dimaya, announced today. In this case, Justice Gorsuch joined the Court’s four “liberals” in a 5–4 decision holding unconstitutional a provision of the Immigration and Nationality Act, which renders deportable any alien convicted of an “aggravated felony.” This statutory phrase is defined to include a “crime of violence,” which itself is defined to include both crimes where use or threat of force is an element, as well as “any other offense that is a felony and that, by its nature, involves a substantial risk that physical force against the person or property of another may be used in the course of committing the offense.” It was this last provision — the “residual clause” of the statute — that was at issue in the case. The majority held that this abstract definition was “impermissibly vague,” and thus a violation of the Fifth Amendment’s Due Process Clause.

In his separate opinion, Justice Gorsuch gave a detailed analysis of the history and legal foundations of the void-for-vagueness doctrine (largely in response to Justice Thomas, who questioned the propriety of this constitutional doctrine both here and in a similar prior case, Johnson v. United States). His concurrence argues that courts must review and strike down unconstitutionally vague statutes, not just to ensure fair notice to potential defendants, but also to enforce the separation of powers between the branches of government:

Under the Constitution, the adoption of new laws restricting liberty is supposed to be a hard business, the product of an open and public debate among a large and diverse number of elected representatives. Allowing the legislature to hand off the job of lawmaking risks substituting this design for one where legislation is made easy, with a mere handful of unelected judges and prosecutors free to “condem[n] all that [they] personally disapprove and for no better reason than [they] disapprove it.”

Justice Gorsuch also made clear that subjecting vague statutes to meaningful judicial review is equally important in civil cases, where penalties are often at least as harsh as they are under the criminal law:

[I]f the severity of the consequences counts when deciding the standard of review, shouldn’t we also take account of the fact that today’s civil laws regularly impose penalties far more severe than those found in many criminal statutes? Ours is a world filled with more and more civil laws bearing more and more extravagant punishments. Today’s “civil” penalties include confiscatory rather than compensatory fines, forfeiture provisions that allow homes to be taken, remedies that strip persons of their professional licenses and livelihoods, and the power to commit persons against their will indefinitely. Some of these penalties are routinely imposed and are routinely graver than those associated with misdemeanor crimes—and often harsher than the punishment for felonies.

This analysis obviously has implications reaching far beyond the immigration context, and is encouraging for those concerned with overcriminalization and arbitrary law enforcement in general. Justice Gorsuch correctly notes that “[p]erhaps the most basic of due process’s customary protections is the demand of fair notice.” But today, we have so many criminal laws that it’s impossible to even count them all: at the federal level alone, we estimate that there are about 4500 criminal statutes, and around 300,000 regulatory crimes — many of which do not involve inherently wrongful conduct and lack any “mens rea” requirement (that is, you can be found guilty even if you had no idea you were acting unlawfully). Who could possibly claim that such a system gives the ordinary citizen “fair notice” of the conduct for which they can be punished?

This degree of overcriminalization also places enormous unchecked power in the hands of law enforcement and prosecutors. As Justice Gorsuch recognized, vague and expansive laws “invite the exercise of arbitrary power … by leaving the people in the dark about what the law demands and allowing prosecutors and courts to make it up.” The staggering breadth of substantive criminalization today means that almost everyone is a criminal, whether they know it or not. If police and prosecutors are inclined to go after you, there’s almost certainly something they can find — whether or not that conduct is genuinely wrongful or harmful.

On the whole, Justice Gorsuch’s opinion in this case is an encouraging sign that he’s aware of and attuned to this set of concerns. Hopefully the newest member of the Court will continue to apply this level of exacting review to vague and arbitrary statutes across the board.