Twitter announced yesterday that they’ll be enforcing a new policy that will allow for reactive blocking of content on a country-by-country basis, and already today some users are vowing to stop using the social media site on Saturday in protest.

The new rule was announced on the company’s blog, and says that specific tweets will be blocked in countries where that content is in violation of the local laws, reports the Washington Post.

“Starting today, we give ourselves the ability to reactively withhold content from users in a specific country — while keeping it available in the rest of the world,” the Twitter post read, in part. “We have also built in a way to communicate transparently to users when content is withheld, and why.”

This kind of policy isn’t new — Google and Facebook also use rules that allow them to remove content in different countries, depending on the laws there that deal with speech. For example, Germany does not allow any pro-Nazi content.

But opponents of Twitter’s rule are worried it will limit the ability of people to organize and come together in times of social upheaval, like during the Arab Spring. Tweets with hashtags like “#TwitterBlackout” and “#TwitterCensored” have been popping up today as users say they want to know they disagree with Twitter’s new policy.

Here’s how it’ll work: First the company will let the individual know when they have content that is being withheld, followed by a clear notice posted to users in that country. Any users outside the country with the blocked content will still be able to see it.

Which means you could be Tweeting away in one country and have no one there see it, but just outside your borders and around the world, you could have a big audience.

Twitter is going to work with Electronic Frontier Foundation’s joint project web site with several universities, Chilling Effects, to post takedown notices as they occur.

Twitter’s country-specific censorship tool prompts user protest [Washington Post]

Tweets still must flow [Twitter blog]

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