On the opening day of law school, I always counsel my first-year students never to support a law they are not willing to kill to enforce.

Usually, they greet this advice with something between skepticism and puzzlement, until I remind them that the police go armed to enforce the will of the state. And if you resist, they might kill you.

I wish this caution were only theoretical. It isn't. Whatever your view on the refusal of a New York City grand jury to indict the police officer whose chokehold apparently led to the death of Eric Garner, it's useful to remember the crime that Garner is alleged to have committed: He was selling individual cigarettes, or loosies, in violation of New York law.

The obvious racial dynamics of the case — the police officer, Daniel Pantaleo, is white; Garner was black — have sparked understandable outrage. But, at least among libertarians, so has the law that was being enforced. Wrote Nick Gillespie in the Daily Beast: "Clearly, something has gone horribly wrong when a man lies dead after being confronted for selling cigarettes to willing buyers." Republican U.S. Sen. Rand Paul of Kentucky, appearing on MSNBC, also blamed the statute: "Some politician put a tax of $5.85 on a pack of cigarettes, so they've driven cigarettes underground by making them so expensive."

The problem is actually broader. It's not just cigarette tax laws that can lead to the death of those the police seek to arrest. It's every law. Libertarians argue that we have far too many laws, and the Garner case suggests they're right. I often tell my students that there will never be a perfect technology of law enforcement and that, therefore, it is unavoidable that there will be situations where police err on the side of too much violence rather than too little. Better training won't lead to perfection. But fewer laws would mean fewer opportunities for official violence to get out of hand.

The legal scholar Douglas Husak, in his excellent 2009 book "Overcriminalization: The Limits of the Criminal Law," points out that federal law alone includes more than 3,000 crimes, fewer than half of which are found in the Federal Criminal Code. The rest are scattered through other statutes. A citizen who wants to abide by the law has no easy way to find out what the law actually is — a violation of the traditional principle that the state cannot punish without fair notice.

In addition, Husak writes, an astonishing 300,000 or more federal regulations may be enforceable through criminal punishment in the discretion of an administrative agency. Nobody knows the number for sure.

Husak estimates that more than 70 percent of American adults have committed a crime that could lead to imprisonment. He quotes the legal scholar William Stuntz to the effect that we are moving toward "a world in which the law on the books makes everyone a felon." Too dramatic? Husak points to studies suggesting that more than half of young people download music illegally from the Internet. That has been a federal crime for almost 20 years. These kids, in theory, could all go to prison.

Many criminal laws hardly pass the giggle test. Husak takes us on a tour through bizarre statutes, including the Alabama law making it a crime to maim oneself to gain sympathy, the Florida law prohibiting displays of deformed animals, the Illinois law against "damaging anhydrous ammonia equipment." And then there's the wondrous federal crime of disturbing mud in a cave on federal land. (Be careful where you run to get out of the rain.)

Overcriminalization matters, Husak says, because the costs of facing criminal sanction are so high and because the criminal law can no longer sort out the law-abiding from the non-law-abiding. But it also matters because — as the Garner case reminds us — the police might kill you.

I don't mean this as a criticism of cops, whose job after all is to carry out the legislative will. The criticism is of a political system that takes such bizarre delight in creating new crimes for the cops to enforce. It's unlikely that the New York legislature, in creating the crime of selling untaxed cigarettes, imagined that anyone would die for violating it. But a wise legislator would give the matter some thought before creating a crime.

Husak suggests as one solution interpreting the Constitution to include a right not to be punished. This, in turn, would mean that before a legislature could criminalize a particular behavior, it would have to show a public interest significantly higher than for most forms of legislation.

He offers the example of a legislature that decides "to prohibit — on pain of criminal liability — the consumption of designated unhealthy foods such as doughnuts."

Of course, activists on the right and the left tend to believe that all of their causes are of great importance. Whatever they want to ban or require, they seem unalterably persuaded that the use of state power is appropriate.

That's too bad. Every new law requires enforcement; every act of enforcement includes the possibility of violence. There are many painful lessons to be drawn from the Garner tragedy, but one of them, sadly, is the same as the advice I give my students on the first day of classes: Don't ever fight to make something illegal unless you're willing to risk the lives of your fellow citizens to get your way.