The tragic suicide last week of Aaron Swartz, the visionary Internet activist who helped create Reddit, is being blamed in part on the zeal of the U.S. attorney whose office was prosecuting him for supposed computer crimes.

Professor Lawrence Lessig of Harvard Law School described his close friend Swartz as having been "driven to the edge by what a decent society would only call bullying." Others pointed out that Swartz's alleged offense -- downloading scholarly papers without paying for them -- was essentially victimless. The owner of the database from which the papers were taken chose not to pursue the matter.

The critics have a point. The prosecution of Swartz was ridiculous. But it's a small part of a larger problem. There's far too much prosecution in the U.S. And as the philosopher Douglas Husak points out in his book "Overcriminalization," the reason we have too much prosecution is that we call too many things crimes.

By one common estimate, Congress creates new federal felonies at the rate of one a week. Husak argues that criminal liability has become less the outcome of deliberation than a habit, a bizarre bit of boilerplate tacked onto the end of statutes or regulations without a second thought. Criminal defense lawyers are fond of claiming that the average American commits two or three punishable crimes every day.

Overbroad Statutes

Here is the nub of the problem, as Husak describes it:

"Experts in the criminal law cannot make accurate predictions about potential offenders because the fate of such persons is not a function of the law at all. The real criminal law, as Holmes would construe it, is formulated by police and prosecutors. The realization that police and prosecutors wield such discretion is nothing new. What is new is the power to arrest and prosecute nearly everyone -- a power that derives from the ever-expanding scope of criminal statutes as written."

The Computer Fraud and Abuse Act -- the principal statute under which Swartz was charged -- is a good example of Husak's point. Enacted in the 1980s, before the Internet explosion, the statute makes a criminal of anyone who "intentionally accesses a computer without authorization or exceeds authorized access" and, in the process, obtains financial information, government information or "information from any protected computer."

What's wrong with this language? Consider: You're sitting in your office, when suddenly you remember that you forgot to pay your Visa bill. You take a moment to log on to your bank account, and you pay the bill. Then you go back to work. If your employer has a policy prohibiting personal use of office computers, then you have exceeded your authorized access; since you went to your bank website, you have obtained financial information.

Believe it or not, you're now a felon. The likelihood of prosecution might be small, but you've still committed a crime.

Aware of this risk, some federal courts have given the statute's language a narrow construction, but others have read it broadly, and the Obama administration has opposed efforts in Congress to narrow its scope. Alex Kozinski, chief judge of the U.S. Court of Appeals for the Ninth Circuit, warned in an opinion last spring that the government's position "would make criminals of large groups of people who would have little reason to suspect they are committing a federal crime."

The statute isn't unique, either in its vagueness or in its scope. In both parties there are people who believe that because they can make something illegal, they should; that somehow they're not showing how much they care unless they're thinking up new reasons to lock people up.

Overzealous Prosecutors

A traditional check on the absurd breadth of the law has been the discretion of prosecutors not to prosecute. Yet as law Professor Angela J. Davis of the American University Washington College of Law notes, this discretion is too rarely exercised.

In her thoughtful book "Arbitrary Justice," reflecting on her own days as a prosecutor, Davis writes that although some colleagues "saw themselves as ministers of justice and measured their decisions carefully, very few were humbled by the power they held." Further, she writes, there's no real check on abuse: "The judicial branch has failed to check prosecutorial overreaching, and the legislative branch traditionally has passed laws that increase prosecutorial power."

In a better world, prosecutors, like other functionaries of government, would indeed be humbled rather than emboldened by the authority placed in their hands. Too often, they're not. The question is what to do about it.

When corporate titans begin to swagger, the response of our political branches is to burden them with layer upon layer of regulation -- including, in many cases, criminal liability. When government officials abuse their authority, even when they cause enormous injury, the usual response is -- nothing. Errors of judgment by private citizens are occasion for new laws; errors by public servants, which can be equally if not more costly, are unfortunate incidents.

Here criminal prosecution presents a particular dilemma. On the one hand, prosecutors need to be able to do their difficult and often dangerous work without constantly looking over their shoulders, worrying about the legal consequences to themselves. On the other, given the penchant of government to criminalize more and more behavior, those who prosecute the law have to display enough common sense and humility to show that they remember they work for us -- not the other way around.

Uncontrolled prosecutors shouldn't necessarily be thrown in jail. But if we believe our own rhetoric about the treatment of others who abuse power, a heightened degree of civil liability would help them to do their jobs better. Right now, prosecutors are protected from most lawsuits by what's called qualified immunity. Prosecutors have to make hard decisions about going after dangerous people. They shouldn't have to worry overmuch about being sued. The immunity of prosecutors should indeed be high. It just shouldn't be as high as it is now.

Unconcerned Judges

And how high is that? High enough that the Supreme Court recently rejected a lawsuit against a prosecutor whose office deliberately failed to turn over exculpatory material to a defendant who was subsequently convicted twice, both times wrongly -- first of armed robbery, then of murder -- and came within a month of execution before the hidden reports turned up. Oh, well, wrote the justices: It was a single incident, not a pattern, and so didn't rise to a violation of the Constitution.

Critics excoriated the decision, but the true problem isn't judicial. It's legislative. Congress could abrogate the immunity of federal prosecutors any time it likes; state legislatures could do the same for their own state's attorneys. Working out a more nuanced system, protecting discretion while allowing lawsuits in cases of clear abuse, would be difficult. But that's no excuse for not trying. Yes, the potential for liability would make the work of the prosecutor harder -- but surgeons and chief executive officers seem to manage.

Prosecutors do need immunity. They just need a little less of it.

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Stephen L. Carter is a Bloomberg View columnist and a professor of law at Yale University. He is the author of "The Violence of Peace: America's Wars in the Age of Obama," and the novel "The Impeachment of Abraham Lincoln."