CHICAGO — U.S. Attorney Andrew Boutros announced Thursday in a Chicago courtroom that he would dismiss the remaining charges with prejudice against four activists who had protested outside a federal building during last year's immigration crackdown. The decision, which prevents the charges from being refiled, came after a closed-door meeting over redacted grand jury transcripts.

Boutros told U.S. District Judge April Perry that he had been unaware until recently of alleged grand jury misconduct by his office, including a prosecutor meeting with a grand juror outside proceedings and preventing jurors who disagreed with dismissing the case from participating. Boutros did not dispute the allegations, calling the conduct upsetting and the reason the case was being dismissed.

"No one acted with the intent to mislead your honor, and I think that they were following your order to give the law," Boutros said. He declined to comment further Thursday through a spokesman.

Perry closed part of the hearing to the public because it involved grand jury proceedings. She also floated the idea of a separate hearing on possible sanctions for the U.S. Attorney's Office over its actions.

The case had been slated to go to trial the following week. Each of the four activists faced a single misdemeanor count of forcibly impeding a federal agent. The defendants included onetime Democratic congressional candidate Kat Abughazaleh, Andre Martin, Brian Straw and Michael Rabbitt. Martin was on Abughazaleh's campaign staff, Straw was an Oak Park village trustee, and Rabbitt was a Democratic committeeperson.

In October, Abughazaleh was among six people initially charged with conspiring to impede an officer, a felony. Prosecutors alleged the activists surrounded an immigration agent's van with other protesters at a federal facility in Broadview, a suburb of Chicago. Charges were later dropped against two of the six. Last month, prosecutors scrapped the felony conspiracy charge altogether as questions emerged about the grand jury transcripts, and fresh charging documents did not detail further allegations against the activists. Defense attorneys said they would seek copies of the unredacted grand jury transcripts to learn more.

"The revelations of the grand jury misconduct that led to the dismissal of the charges is sadly not surprising," said Abughazaleh's defense attorney Josh Herman. "This misguided case should have never been brought against Kat Abughazaleh or any of her co-defendants for exercising their protected First Amendment rights."