At age 3, most toddlers know how to play make-believe, turn the pages of a book, and spontaneously show affection for their friends. But can 3-year-olds possibly grasp the fundamentals of the American justice system and defend themselves in court?

Judge Jack Weil believes so. The Virginia-based judge is a key witness supporting the US government’s position that unaccompanied migrant youths don’t need attorneys in immigration court, while immigration advocates argue otherwise.

"I've taught immigration law literally to 3-year-olds and 4-year-olds. It takes a lot of time. It takes a lot of patience," Judge Weil said. "They get it. It's not the most efficient, but it can be done."

As the number of unaccompanied and undocumented children attempting to cross the southern American border has skyrocketed in recent years, advocates say that they should not be sent back their home countries, where gang violence and poverty are the reasons for their departure.

According to Thomas Homan, the head of Immigration and Customs Enforcement's removal operations, 7,643 child immigrants were deported between 2012 and 2015. But in that same period, Mr. Homan told the Senate Judiciary Committee, more than 171,000 children were apprehended at the border. Most of them came from Honduras, El Salvador, and Guatemala.

The biggest migration spike took place in 2014. When they arrive at the border, the majority of unaccompanied children are immediately apprehended, processed, and initially detained by Customs and Border Patrol. If they come from countries such as El Salvador, Guatemala, or Honduras, the youths are placed into standard removal proceedings in immigration court.

And after being screened by a CBP officer to determine of they are victims of trafficking or persecution back home, these children are transferred into the custody of the Office of Refugee Resettlement under Health and Human Services within three days.

But in the standard removal proceedings, undocumented children and families have no guarantee of counsel in court – not even for 3-year-olds.

Just last month, Democrats in Congress introduced a bill that would grant attorneys for children in immigration court who came to the border alone or were victims of abuse, torture, and violence.

The legislation comes at the heels of a 2014 class-action lawsuit filed by the American Civil Liberties Union and several other groups, pursuing in a Seattle federal court the right of unaccompanied youths to have court-appointed counsel.

The plaintiffs claim that the Justice Department, including the immigration courts and other federal immigration agencies, violated due process and the children’s right to a fair trial under the Immigration and Nationality Act.

The deposition in which Weil says toddlers can defend themselves in court was submitted to the court by the federal government in January. The ACLU posted the transcript on Friday.

“Are you aware of any experts in child psychology or comparable experts who agree with the assessment that 3- and 4-year-olds can be taught immigration law?" Ahilan Arulanantham, the deputy legal director of the ACLU of Southern California, asked Weil in the transcript.

"I haven't read any studies one way or another," Weil answered. “I have trained 3-year-olds and 4-year-olds in immigration law,” he later maintained. “You can do a fair hearing."

But even the federal government has questioned the credibility of Weil’s stance. Although the Justice Department is currently in the throes of the lawsuit, spokeswoman Lauren Alder Reid told the Los Angeles Times in a statement that the administration is actually in support of the Congressional legislation providing representation for youth migrants.

"The assistant chief immigration judge was speaking in a personal capacity when he made that statement,” Ms. Reid said. “The Department of Justice recognizes that immigration court proceedings are more effective and efficient when individuals are represented.”

The next court hearing is set for March 24, Mr. Arulanantham says. Meanwhile, the influx of immigrant children into the US is expected to break records yet again in 2016.