NEW YORK – Twitter, a tool of choice for dissidents and activists around the world, found itself the target of global outrage Friday after unveiling plans to allow country-specific censorship of tweets that might break local laws.

It was a stunning role reversal for a youthful company that prides itself in promoting unfettered expression, 140 characters at a time. Twitter insisted its commitment to free speech remains firm and sought to explain the nuances of its policy, while critics – in a barrage of tweets – proposed a Twitter boycott and demanded that the censorship initiative be scrapped.

In China, where activists have embraced Twitter even though it’s blocked inside the country, artist and activist Ai Weiwei tweeted in response to the news: “If Twitter censors, I’ll stop tweeting.”

One often-relayed tweet bore the headline of a Forbes magazine technology blog item: “Twitter Commits Social Suicide”

San Francisco-based Twitter, founded in 2006, depicted the new system as a step forward. Previously, when Twitter erased a tweet, it vanished throughout the world. Under the new policy, a tweet breaking a law in one country can be taken down there and still be seen elsewhere.

Twitter said it will post a notice whenever a tweet is removed and will post the removal requests it receives from governments, companies and individuals at the website chillingeffects.org.

The critics are jumping to the wrong conclusions, said Alexander Macgilliviray, Twitter’s general counsel.

“This is a good thing for freedom of expression, transparency and accountability,” he said. “This launch is about us keeping content up whenever we can and to be extremely transparent with the world when we don’t. I would hope people realize our philosophy hasn’t changed.”

Some defenders of Internet free expression came to Twitter’s defense.

“Twitter is being pilloried for being honest about something that all Internet platforms have to wrestle with,” said Cindy Cohn, legal director of the Electronic Frontier Foundation. “As long as this censorship happens in a secret way, we’re all losers.”

But Reporters Without Borders, which advocates for press freedom, sent a letter to Twitter’s executive chairman, Jack Dorsey, urging that the censorship policy be ditched immediately.

“By finally choosing to align itself with the censors, Twitter is depriving cyberdissidents in repressive countries of a crucial tool for information and organization,” the letter said. “Twitter’s position that freedom of expression is interpreted differently from country to country is unacceptable.”

Twitter said it has no plans to remove tweets unless it receives a request from government officials, companies or another outside party that believes the message is illegal. No message will be removed until an internal review determines there is a legal problem, according to Macgilliviray.

“It’s a thing of last resort,” he said. “The first thing we do is we try to make sure content doesn’t get withheld anywhere. But if we feel like we have to withhold it, then we are transparent and we will withhold it narrowly.”