The American Civil Liberties Union has filed a complaint with the U.S. Justice Department alleging that the Border Patrol violated the Voting Rights Act when it scheduled a “crowd control exercise” for Election Day near an almost exclusively Hispanic El Paso neighborhood. The exercise was scrapped amid heavy criticism from members of Congress and voting rights groups, but the ACLU contends the damage was already done.

“Voter intimidation has no place in our elections and is illegal. Yet the Border Patrol was planning to proceed with this intimidating crowd control exercise for no good reason on Election Day,” Sophia Lin Lakin, staff attorney for ACLU Voting Rights Project, said in a statement. “We are asking that the DOJ investigate that decision, particularly in light of President Trump’s menacing tweet yesterday calling for law enforcement to aggressively monitor supposed concerns about mythical illegal voting.”

The Department of Homeland Security did not immediately respond to a request for comment on the complaint. The ACLU’s complaint doesn’t cite any specific evidence of voters saying they felt intimidated by the planned exercise. “I’m not aware of any particular individuals that were deterred from voting, although it’s not a stretch to believe that a military-style exercise with armored units would be intimidating or threatening to voters—whether or not they ultimately voted,” Lakin said. “In any event, a voter being actually deterred from casting a ballot is not something that we need to show with respect to asking the DOJ to investigate the Border Patrol’s decision and announcement as potential voter intimidation. The question is whether the activity is intimidating to voters, and we believe there is, at a minimum, a sufficient basis here to warrant an investigation.”

The El Paso Border Patrol Sector issued a press release on Monday announcing plans for the exercise the following day at an international railroad crossing that abuts Chihuahuita, a historic and almost exclusively Hispanic neighborhood that sits against the border fence. El Paso is also the hometown of Democratic candidate for U.S. Senate Beto O’Rourke, who was still mounting a strong, albeit unsuccessful, effort to upset incumbent Senator Ted Cruz on Election Day.

Texas Monthly first reported those plans Monday night in a story that included sharp criticism from several Texas Democratic congressmen and the ACLU. Other voting rights groups also criticized the plan Tuesday morning. 

The Border Patrol decided to postpone the exercise to a later date just minutes before its scheduled start. The agency had already moved in equipment, including horses and military-style vehicles, before making the decision to postpone.

“On the morning of November 6, Border Patrol vehicles and armored units were observed driving within this area,” the ACLU said in its complaint to the Justice Department. “After mounting concerns and complaints, shortly before the exercise was set to begin, Border Patrol employees informally told media and community organizations, including the ACLU, that the exercise had been cancelled, but did not immediately issue a formal statement to that effect. Though cancelled at the last minute, the announcement of this exercise itself appears to be an attempt to intimidate voters in the Latinx community, and the delay in issuing a formal announcement of the cancellation demonstrates that the Border Patrol did not intend for voters to be relieved of the fears caused by the initial announcement.”

The Border Patrol has been doing numerous exercises in recent days in El Paso and other border communities as part of planning for the arrival of a caravan of Central American migrants now making its way through Mexico. The migrants have said they plan to seek asylum at the border. On October 29, Customs and Border Protection officers stopped traffic at the Paso del Norte Bridge in El Paso as other officers in riot gear practiced a response to the caravan arrival. Unlike that exercise, the one planned for Election Day would have occurred away from the bridge and port of entry and near a residential area.

The Border Patrol issued a news release late Monday explaining the reasons for postponement of the Election Day exercise. “The U.S Border Patrol’s El Paso Sector postponed joint caravan-related exercises on the El Paso border scheduled for today out of an abundance of caution and due to inaccurate reporting that caused unneeded confusion in border communities. We will continue training exercises in the following days, as necessary to ensure border security and the safety of the American people, the traveling public, CBP personnel and the communities in which we serve.”

The agency didn’t respond to questions about what was inaccurate in the reporting. A Department of Homeland Security spokesman in Washington spoke at length with a Texas Monthly reporter on Tuesday morning and raised no claims of inaccurate reporting.

The ACLU complaint said the planned exercise was alarming in the current political environment, including  “the Trump Administration’s repeated threats and targeted actions against immigrant communities, including by Border Patrol specifically,” the complaint said.

The section of the Voting Rights Act cited by the ACLU says, “No person, whether acting under color of law or otherwise, shall intimidate, threaten, or coerce, or attempt to intimidate, threaten, or coerce any person for voting or attempting to vote …” The law allows the Justice Department to bring a civil suit against any person or agency it believes violated the law. The Justice Department is currently overseen by Attorney General Jeff Sessions, but with news of Session’s resignation on Wednesday, Trump is expected to appoint a new attorney general soon.