SEOUL, South Korea – Attacks on basic freedoms are nothing new on the Korean peninsula. Material considered a threat to state security is routinely deleted, and citizens who openly criticize the government find themselves ostracized, and sometimes imprisoned.

For once, though, the discussion does not center on North Korea, where the brutal quashing of dissent is the stock in trade of the Pyongyang regime. This time, the focal point is on free and democratic South Korea, where the government stands accused of using the law to silence dissenters 25 years after the country emerged from decades of military dictatorship.

Park Jeong Keun apparently had no idea anything was amiss when he entertained his Twitter followers with satirical sideswipes at North Korea. But the humorous intent behind his retweets of self-evidently ludicrous missives from the regime's own Twitter account was lost on the authorities in the South.

The 23-year-old photographer, who was indicted in February, now faces a possible prison sentence after being charged with "praising and supporting an enemy of the state" under a law introduced more than six decades ago to protect the new South Korea from communist infiltration.

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"This is not a national security case; It's a sad case of the South Korean authorities' complete failure to understand sarcasm," Sam Zarifi, Asia-Pacific director of Amnesty International, said after Park's arrest earlier this year.

"Imprisoning anyone for peaceful expression of their opinions violates international law but in this case, the charges against Park are simply ludicrous and should be dropped immediately."

Park, a member of the Korean Socialist Party, was charged under the National Security Law, introduced when South Korea was founded in 1948 to protect the fledgling state against espionage and insurrection from groups sympathetic to the country's communist neighbor.

The law is still frequently used to investigate those who "praise, disseminate or cooperate with anti-state groups," but, critics say, it is also being enlisted in the biggest official assault on free speech since South Korea became a democracy in 1987.

"We have been compiling reports on abuses of freedom of speech since the 1970s, and the security law has featured every time," says Park Jin Ok, manager of Amnesty International Korea. "It represents a serious threat to human rights in South Korea."

South Korea's conservative president, Lee Myung Bak, defended the law, which he said was needed to address the threat from North Korean spies and sympathizers. "If you consider that fact, and if you are someone living in such a country every day, then you will understand the need to have such laws that will allow us to maintain our way of life," he said in an interview with National Public Radio.

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But Park Jeong Keun's case is typical of how easily the law can be abused, says Amnesty's Park. "The point here is not whether the charges stand up, but how the government is using the law to control public discourse and make people think twice before expressing an opinion. It's creating a climate of fear.

"Many people don't even know the law still exists until they are charged with something. In the past it applied only to pro-North Korean groups, but now individuals are being targeted."

Early attempts to abolish the law failed due to anti-North Korean sentiment fomented by the 1950-53 Korean War, and again in 2007, when the threat from the North's missile and nuclear programs was deemed serious enough to keep it on the statute books.

The number of cases has risen dramatically under the Lee administration. In 2007, the year he became president, police interrogated 39 people on suspicion of violating the national security law; in 2010 the number had risen to 151.

Legal actions against people who post "pro-North Korean" material on line have soared, from just five in 2008 to 82 in 2010, according to the government. That has coincided with a dramatic rise in the number of deletions of online posts deemed to be supportive of the Pyongyang regime.

When the National Security Law doesn't apply, the Lee administration has used other methods to take on detractors in a way that critics say is the legal equivalent of cracking a nut with a sledgehammer.

Late last year, Chung Bong Ju was jailed for a year for defamation after spreading rumors about alleged stock fraud involving President Lee going back to 2007. Chung was more than just a nuisance; by the time he was arrested he was arguably the president's most formidable nemesis as one of four co-hosts of "Naneun Ggomsuda," ("I'm a petty-minded creep"), a wildly popular podcast that used humor and liberal doses of bad language to heap ridicule on the government in Seoul.

The weekly online talk show built up a huge following after its launch in April 2010, and quickly became one of the most downloaded political podcasts on iTunes. Chung's supporters claim the verdict was politically motivated, coming months before national assembly elections in April in which Lee's party faced a resurgent opposition.

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In a report published last year, Frank La Rue, the United Nations' special rapporteur on the freedom of opinion and expression, warned that "the space for freedom of expression in [South Korea] has been shrinking in recent years."

He voiced concern that "many criminal defamation suits are filed for statements that are true and are in the public interest, and used to penalize individuals who express criticisms of the government."

Journalists say the erosion of freedoms taken for granted in liberal democracies has seeped into the broadcast media, where more than 1,000 union members have been on strike since early this year in protest at government interference in news coverage.

The dispute centers on Korean Broadcasting System (KBS), which strikers accuse of pro-government bias under its president, Kim In Kyu, who helped with Lee Myung Bak's election campaign in 2007. KBS and staff from other broadcasters have called for Kim and "politically appointed" executives from other networks to be replaced, for sacked union members to be reinstated and for the return of "fairness and justice" to South Korean journalism through changes to the broadcasting law.

A spokesman for the National Union of Media Workers told GlobalPost that close ties between the Lee government and senior TV executives had "corrupted" South Korean journalism.

"Our action is intended to put an end to the destruction of proper reporting and restore our viewers' right to know," said the spokesman, who did not wish to be named. "Freedom of the press in South Korea is worse now than it was even under the military dictatorships of the 1960s and 1970s."