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The Justice Department is demanding that the website-hosting company DreamHost turn over identifying information on visitors to a website used to organize protests during the president’s inauguration in January. The company, which is fighting the request in court, believes the search warrant is unconstitutionally broad and a threat to free speech. And digital privacy advocates warn that it could represent a McCarthyesque strategy for identifying political dissidents opposed to President Donald Trump and his administration.

In a blog post Monday, DreamHost revealed its ongoing legal battle with the Justice Department. The department, in what appears to be part of its investigation into anti-Trump protests that turned violent on Inauguration Day, served DreamHost with a search warrant on July 12 related to its hosting of the protest organizing site disruptj20.org (a reference to the January 20 inauguration). The company views the warrant’s request for information on site visitors as overly broad. “Chris Ghazarian, our General Counsel, has taken issue with this particular search warrant for being a highly untargeted demand that chills free association and the right of free speech afforded by the Constitution,” the company wrote. “This is, in our opinion, a strong example of investigatory overreach and a clear abuse of government authority.”

The Trump administration appears to be cracking down on people who speak about against it. In February, the Justice Department handed down charges against more than 200 protesters arrested on Inauguration Day; two months later, it increased the severity of those charges to include charges for inciting rioting, conspiracy to riot, and destruction of property. In March, US Customs and Border Protection sought records from Twitter in order to unmask the people behind an account that purported to share the views of civil servants who disagree with the president’s policies. Twitter sued in order to keep the information secret, and the government ultimately dropped the request. In May, the Justice Department put a woman on trial for laughing during Attorney General Jeff Sessions’ Senate confirmation hearing. Department lawyers argued that the laugh constituted “disorderly and disruptive conduct” meant to “impede, disrupt, and disturb the orderly conduct” of Congress.

The DreamHost warrant comes from the same jurisdiction and covers the same material as the Justice Department’s ongoing prosecution of the inauguration protesters, so it’s likely part of the same effort, though the affidavit behind the warrant is not public. “I think it’s reasonable to assume that it’s connected to that prosecution,” says Stephanie Lacambra, a criminal defense attorney with the Electronic Frontier Foundation, an advocacy group dedicated to civil liberties in the digital realm. Lacambra says that the warrant could mean that department prosecutors are struggling to shore up a weak case against the protesters.

“Perhaps they don’t know if they are prosecuting the right people?” she says. “The Fourth Amendment requires them to be able to identify specifically what it is they are looking for and why they are looking for it—that’s what probable cause means. And the fact that they are identifying an entire class of people, anyone who clicked on the website, that to me highlights the fact that they don’t actually know who to charge with what.” (My name would most likely appear on the list the Justice Department is seeking, since I visited the website during my coverage of the inauguration protests.)

Last Friday, DreamHost filed a court motion in Washington, DC, arguing that the warrant is unconstitutionally broad under the First and Fourth Amendments. The requested records would provide the government with a list of identifying information on all the website’s visitors, including “the time and date of the visit, the IP address for the visitor, the website pages viewed by the visitor (through their IP address), and even a detailed description of the software running on the visitor’s computer,” DreamHost says in its motion. “Courts have specifically held that the government oversteps its authority when it seeks to obtain customer identities and records of activity in connection with protected speech, such as that involved here,” the motion continues. “United States Supreme Court cases ‘insist that the courts apply the warrant requirements with particular exactitude when First Amendment interests would be endangered by the search.'”

The DreamHost warrant, if the court upholds the request, could be used to find and prosecute political opponents of President Donald Trump—or at least send a chilling message to those thinking of protesting the president in the future. Even visiting a protest website, under this warrant, could make someone a person of interest. “Once the [Justice Department] has access to this information, there is nothing that prevents them from being able to identify whole swaths of the population that may be less than thrilled with the current administration,” says Lacambra, calling such a possibility a “throwback to McCarthyism,” when the government targeted people for their political affiliations. It’s unclear exactly how the government might use this information—or information gathered through similar warrants in the future—but as Lacambra points out, the Justice Department has already shown it will use its “discretion to target political dissidents.”

“This is going to have far-reaching implications for the exercise of First Amendment rights,” she adds. “We should really perk up and pay attention, because it has some pretty severe consequences for everybody.”

The next step is a hearing in DC Superior Court on Friday, August 18.