The acting president of the Journalists Association of Samoa said the criminal libel law enacted this week risks undermining the role of the media in society.
Rudy Bartley said he's concerned the legislation will be used to force journalists to expose sources.
The government said the Criminal Libel Act targets unidentified bloggers who write defamatory remarks about others.
One such blogger, O Le Palemia, regularly attacks the government of Tuilaepa Sa'ilele Malielegaoi with accusations of corruption and nepotism.
But according to Mr Bartley, the criminal libel law will be ineffective in identifying such individuals.
He said it's also unnecessary for the mainstream media which has recently adopted a code of practice to prevent criminal libel law breaches by members.
Mr Bartley argues the law will undermine the media's role as a public watchdog and weaken its ability to hold those in power to account.