One of the most heated moments during Wednesday evening’s Democratic presidential debate was an unexpected confrontation between two candidates from Texas over an obscure component of US federal law that has broad ramifications over America’s immigration system.

Julián Castro, the former Secretary of Housing and Urban Development, and former Rep. Beto O’Rourke sparred over Section 1325 of the US Code and how it has impacted the influx of Central American asylum-seekers over the last year.

The confrontation started after O’Rourke vowed not to build walls, cage migrant children, separate families, or criminally prosecute families seeking asylum in the US.

But Castro quickly interrupted, arguing that O’Rourke supports Section 1325, and therefore couldn’t uphold his promise not to criminally prosecute migrant families.

Section 1325 was implemented in 1929 and made it a criminal offence to illegally enter the US, rather than just a civil offence.

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That distinction is significant – it means a migrant who crosses the border illegally can be charged with a federal misdemeanour, jailed, fined, and deported. Meanwhile, other unauthorised immigrants who may have entered the US legally but overstayed their visas are merely committing civil violations, akin to simple traffic violations.

The code reads:

“Section 1325 sets forth criminal offenses relating to (1) improper entry into the United States by an alien, (2) entry into marriage for the purpose of evading immigration laws, and (3) establishing a commercial enterprise for the purpose of evading immigration laws.”

“Let’s be very clear. The reason that they’re separating these little children from their families is that they’re using Section 1325 of that act, which criminalizes coming across the border to incarcerate the parents and then separate them,” Castro said during the debate. “Some of us on this stage have called to end that section, to terminate it. Some, like Congressman O’Rourke, have not. And I want to challenge all of the candidates to do that.”

The “zero tolerance” policy that the Trump administration implemented in the spring of 2018 attempted to use Section 1325 to prosecute 100% of the adults illegally crossing the US-Mexico border.

Before the “zero tolerance” policy, authorities used discretion at the border and generally only prosecuted migrants who had extensive criminal records or were suspected of human trafficking or gang ties.

But the heightened rigour from “zero tolerance” meant that all adults who were prosecuted for the illegal entry misdemeanour had to be brought before a judge and jailed, thereby separating them from any children they had arrived with, since federal law also prohibits children from being detained with their parents.

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Since the bulk of the migrants apprehended at the border in recent years have come as part of family units, the policy resulted in untold thousands of children forcibly separated from their parents.

O’Rourke has previously defended Section 1325, telling CNN’s Jake Tapper in a June 16 interview that the law was necessary to hold certain criminals accountable.

“If somebody is attempting to smuggle human beings into the United States, if they are attempting to cross illegal drugs into this country, I want to make sure that we have the legal mechanism necessary to hold them accountable and to detain them to make sure that they do not pose a threat to this country or to our communities,” O’Rourke said on CNN.

During the debates, Castro argued that other sections of the US Code already cover those concerns.

“I think that you should do your homework on this issue,” Castro told O’Rourke. “If you did your homework on this issue, you would know that we should repeal this section.”

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