Criminal defamation laws are stupid. But they're more than stupid: they're harmful. Plenty of entire countries still have them. But those countries don't have a First Amendment. With the First Amendment in place, it makes little sense to criminalize speech that can be handled through civil litigation. Nevertheless, these outdated laws are still on the books. In some cases, courts have already found them unconstitutional, but legislators seem unwilling to remove laws that are only ever abused by the government.
Due to this combination of laziness and self-interest, half the country still allows the government to arrest people for engaging in alleged defamation. One of those 25 states is New Hampshire, where the ACLU is now working to have the law ruled unconstitutional.
The case stems from the arrest of New Hampshire resident Robert Frese. Frese was hauled in by Exeter cops for calling the Exeter police chief "corrupt" and saying that he had "covered up" for dirty Exeter cops. The arrest of Frese for criticizing Exeter law enforcement did nothing to undermine either of his claims. If anything, it just made Exeter cops look dirtier and Police Chief William Shupe look more corrupt.
The criminal defamation charges ended up being dropped by the prosecutor, who found the charge wasn't worth pursuing. That ended this criminal prosecution under the stupid state law, but it didn't get rid the stupid state law that allowed Police Chief Shupe to retaliate against Frese in the first place.
That's where the ACLU comes in. Suing on behalf of Frese (and New Hampshire residents in general), the ACLU points out in its lawsuit [PDF] that criminal defamation laws are mainly used by government officials to shut down criticism or otherwise punish members of the public.
Nationally, criminal defamation charges are disproportionately filed against people who criticize public officials or government employees, especially law enforcement officers. One study identified 23 criminal defamation prosecutions or threatened prosecutions for the period from 1990-2002, 12 of which were deemed “political,” and 20 of which involved public figures or issues of public controversy. George C. Lisby, No Place in the Law: The Ignominy of Criminal Libel in American Jurisprudence, 9 Comm. L. & Pol’y 433, 467 (2004) (citing Russell Hickey, A Compendium of U.S. Criminal Libel Prosecutions: 1990-2002, Libel Defense Resource Center Bull., Mar. 27, 2002, at 97)). Another study, focusing on Wisconsin, found that 39 percent of criminal defamation prosecutions involved either public officeholders or government employees, including numerous charges of sexual misconduct by law enforcement and probation officers. David Pritchard, Rethinking Criminal Libel: An Empirical Study, 14 Comm. L. & Pol’y 303, 327– 33 (2009).
More specific examples can be found at the ACLU's website:
The editor and publisher of a small newspaper in Kansas were convicted of criminal defamation after the paper published an article suggesting that the mayor lived in another county and was therefore ineligible for public office. A Massachusetts woman was convicted of criminal defamation in New Hampshire after she claimed that a coffee shop’s employees spit in police officers’ coffee. And a Kansas man was charged with criminal defamation after he posted a yard sign criticizing his local government’s inaction on a water drainage problem…
Keeping an obviously-unconstitutional law on the books gives government more hammers to deploy against pesky nails who won't keep their heads down. Citizens -- who rarely have the power to remove laws from the books -- continue to be the victims of bad lawmaking and the bad lawmakers who benefit from them.