The FBI is monitoring groups on the border that are protesting U.S. immigration policy, according to a document obtained by Yahoo News.

The FBI has gathered intelligence from people with “direct access” to the organizations and is monitoring their social media, according to the document,  called an “external intelligence note,” that was obtained by Yahoo News. The note, which was produced by the FBI office in Phoenix and sent to other law enforcement and government agencies, said there are indications these groups are “increasingly arming themselves and using lethal force to further their goals.” However, almost all of the evidence cited in the report involved nonviolent protest activity.

The intelligence collected and cited in the FBI document, dated May 30, 2019, is worrisome to activists and civil rights advocates who say that the government is classifying legitimate government opposition and legally protected speech as violent extremism or domestic terrorism.

“The document raises potential legal concerns in a gray area not yet tested by the courts,” Geoffrey Stone, a University of Chicago law professor, told Yahoo News.

“If you’re investigating antiwar and anti-Trump groups, you run the risk of interfering with free speech rights,” said Stone, who was tapped by President Obama to help review foreign intelligence surveillance programs following the Edward Snowden disclosures.

In a statement to Yahoo News, an FBI spokesperson described the external intelligence note about border protests groups as part of routine information-sharing among law enforcement agencies, and emphasized that it contained the perspective of the Phoenix office.

“These products are intended to be informative in nature,” the FBI spokesperson said. “And as such, they contain appropriate caveats to describe the confidence in the sourcing of information and the likelihood of the assessment. Additionally, when written at a local level, these products will note that the perspective offered may be limited to the field office’s area of responsibility.”

While the external intelligence note on border protest groups was originally generated by the FBI’s Phoenix office, it was distributed widely throughout the bureau and to other law enforcement agencies around the country.

Mike German, a former FBI special agent and fellow at New York University who has written extensively about surveillance of activists, sees the document as evidence of the bureau’s overreach when it comes to classifying domestic groups as terrorist threats.