The FBI on Friday arrested a Wisconsin judge accused of helping a man evade immigration authorities, escalating a clash between Donald Trump's administration and the judiciary over the Republican president's sweeping immigration crackdown.

Hannah Dugan, a Milwaukee County Circuit Court judge, appeared briefly in federal court in Milwaukee on Friday before being released from custody. Her next court appearance is May 15. A crowd formed outside the courthouse, chanting "Free the judge now."

Dugan is charged with obstructing a proceeding and concealing an individual to prevent arrest.

"Judge Dugan wholeheartedly regrets and protests her arrest. It was not made in the interest of public safety," her lawyer, Craig Mastantuono, said during the hearing. He declined to comment to an Associated Press reporter following the court appearance.

Immigration agents showed up to arrest the man, Eduardo Flores-Ruiz, without a judicial warrant outside her courtroom on April 18. Dugan is accused of escorting Flores-Ruiz and his lawyer out of the courtroom through the jury door as a way to help avert his arrest, according to an FBI affidavit filed in court.

The affidavit quotes the courtroom deputy as having heard Dugan say words to the effect of, "Wait, come with me," before ushering them into a non-public area of the courthouse. The action was unusual, the affidavit says, because "only deputies, juries, court staff, and in-custody defendants being escorted by deputies used the back jury door. Defence attorneys and defendants who were not in custody never used the jury door."

WATCH | Protesters call for Dugan's release:

Protesters rally in support of arrested Wisconsin judge

U.S. officials arrested Hannah Dugan, a Milwaukee County circuit judge, on Friday and charged her with helping a man in her court evade immigration authorities. Supporters of the judge gathered outside the federal court where she appeared to face charges, and criticized the Trump administration in its escalating dispute with local officials over immigration enforcement. 'This is incorrect. This is immoral,' said Casey Serrano with the Milwaukee Alliance Against Racist and Political Repression.

Dugan left the courthouse through a side door without comment.

"Judge Dugan will defend herself vigorously, and looks forward to being exonerated," a publicity firm said on her behalf.

FBI director Kash Patel said in a post that was later deleted that immigration officials had been attempting to apprehend Flores-Ruiz, whom he described as an "illegal alien." Patel said agents later caught up to Flores-Ruiz and detained him.

Democratic Sen. Tammy Baldwin of Wisconsin said Dugan's arrest is a "gravely serious and drastic move" that "threatens to breach" the separation of power between the executive and judicial branches.

U.S. Attorney General Pam Bondi said the man was facing domestic violence charges and that victims were sitting in the courtroom with state prosecutors when Dugan helped him escape immigration arrest.

The complaint said Flores-Ruiz had previously been deported to Mexico.

"Since President Trump was inaugurated, activist judges have tried to obstruct President Trump and the American people's mandate to make America safe and secure our homeland," Department of Homeland Security spokesperson Tricia McLaughlin said in a statement, "but this judge's actions to shield an accused violent criminal illegal alien from justice is shocking and shameful."

The Justice Department in January ordered prosecutors to investigate for potential criminal charges against state and local officials who obstruct or impede federal functions. As potential avenues for prosecution, a memo cited a conspiracy offence as well as a law prohibiting the harbouring of people in the country illegally.

WATCH | Thousands protest policy as U.S. Supreme Court pauses deportations:

Thousands protest Trump’s policy as Supreme Court pauses deportations

Tens of thousands of protesters rallied across the U.S. over the weekend to denounce President Donald Trump's deportation policies, calling them the end of due process. At the same time, the Supreme Court blocked the removal of migrants the White House planned to deport under a wartime law.

Legal battles over immigration, deportations

The arrest comes as the Trump administration, in about 100 days into its term, has already been fighting pitched battles in the courts, with Democratic opposition, over immigration enforcement.

Federal judges have ordered the U.S. government to facilitate the return of two men who were not only deported to El Salvador but sent to a harsh prison in that country — Kilmar Abrego Garcia, originally from El Salvador, as well as a 20-year-old Venezuelan man, identified only as Cristian.

There have also been lawsuits challenging the government's use of the 1798 Alien Enemies Act as the legal underpinning for some deportations, as well as objections to the detentions of foreign-born students who participated in U.S. protest activity.

WATCH | How an 18th-century law has been utilized by the Trump administration:

How can Trump use a wartime law to deport people when there's no war? | About That

The Trump administration deported more than 200 immigrants by invoking the Alien Enemies Act — a wartime measure — alleging they were members of Tren de Aragua, a Venezuelan gang. Andrew Chang explains how Trump is interpreting the language of the 1798 law in order to avoid the standard immigration court system, and why experts say it's a slippery slope.

In addition, a federal judge on Thursday blocked the Trump administration from withholding federal funding from 16 so-called sanctuary jurisdictions — all outside Wisconsin — that have declined to co-operate with the Republican president's hardline immigration crackdown.

During Trump's first administration, from 2017 to 2021, the Justice Department charged a Massachusetts judge with obstruction of justice on allegations she helped a man who was living in the U.S. illegally sneak out a back door of a courthouse to evade a waiting immigration enforcement agent.

The prosecution of a sitting judge sparked outrage from many in the legal community, who slammed the case as politically motivated.

The case against Newton District Judge Shelley Joseph was dropped in 2022 under the Democratic administration of Joe Biden after she agreed to refer herself to a state agency that investigates allegations of misconduct by members of the bench.

Dugan was first elected as a county judge in 2016, and before that she served as head of the local branch of Catholic Charities, which provides refugee resettlement programs, among other services. She spent much of her early career as a lawyer at the Legal Aid Society of Milwaukee, which serves poor people.

Before being elected to public office, Dugan practised law at Legal Action of Wisconsin and the Legal Aid Society. She graduated from the University of Wisconsin-Madison in 1981 with a bachelor of arts degree and earned her Juris Doctorate in 1987 from the school.