A free speech law center says President Trump and his staff are breaking the law when they block his critics on Twitter. The Knight First Amendment Institute has filed a lawsuit saying the president's Twitter feed is a public forum protected by the First Amendment.

The suit, filed Tuesday, accuses the White House of suppressing dissent by excluding Twitter users who criticize Trump or his policies. It cites recent statements by White House staff that deem tweets from the president's @realDonaldTrump account as official statements, as well as a recent Supreme Court opinion that called Twitter and Facebook "perhaps the most powerful mechanisms available to a private citizen to make his or her voice heard."

The lawsuit was filed by seven people who have been blocked from Trump's account, along with the Knight First Amendment Institute, which is affiliated with Columbia University. The group initially threatened to sue a month ago, when it sent the White House a letter demanding that it stop blocking people who respond critically to the president's messages.

In addition to preventing those citizens from reading and responding to the president's tweets, the group said, the practice violates others' rights to an open forum where they can hear critical debate. The Trump administration did not respond to that letter, the group said.

"The White House is transforming a public forum into an echo chamber," said Katie Fallow, a senior staff attorney at the Knight Institute.

Discussing Trump's Twitter feed last month, Jameel Jaffer, the institute's executive director, told NPR's David Folkenflik, "I don't even think it's arguable. It is the most important social media account operated by the U.S. government or a U.S. government official right now. And it is operated in order to get President Trump's opinions about government policy to Americans and to the world."

After the lawsuit was filed, Jaffer released a statement saying, "The First Amendment applies to this digital forum in the same way it applies to town halls and open school board meetings. The White House acts unlawfully when it excludes people from this forum simply because they've disagreed with the president."

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