Tunisian authorities this week detained labor leader Walid Zarrouk and summoned journalist Zouhaer al-Jiss for issuing statements critical of the government.
Joe Stork, director of Middle East programs at Human Rights Watch, said the government was using the law to limit free speech.
"Instead of trying to silence critics, the government should look into their allegations, and fix the laws from the old repressive government that criminalize criticism of public figures," he said in a statement Friday.
With public support waning, Tunisia has struggled to make enduring political gains since the Jasmine Revolution unseated long-time leader Zine al-Abidine Ben Ali two years ago. The revolution was sparked by the protest suicide of a street vendor in late 2010.
A report published Thursday by the Pew Research Center found Tunisians were frustrated with progress made since the so-called Jasmine Revolution.
The revolution brought the Islamist political party Ennahda to power. The BBC reported Saturday "tens of thousands" of people turned out in the streets of Tunis calling on the Islamist government to disband.
"In Tunisia, the euphoric Arab Spring has descended into a summer of discontent," the Pew report said.