But our border with Mexico cuts across a historically, economically and culturally integrated region, and hardening it doesn’t stop the demand or supply of Mexican and Central American labor. Nor does it much discourage refugees fleeing life-threatening civil violence. Intense militarized enforcement does make border-crossing more perilous, so demand for help getting across — for “trafficking” and “smuggling” — goes up. Ascending to the next rung on the ladder of escalation requires capitalizing on other sources of overreaction to criminalize that help.

Moral panic over trafficking of sex slaves and forced laborers is promoted not only by religious conservatives looking to crack down on consensual sex work and outlaw pornography but also by feminists and liberal Hollywood do-gooders. This climate of alarm has been tremendously useful to reactionary nationalists looking to seal off borders and routes of migration.

This is not to say coerced sex and labor trafficking isn’t a serious and horrifying problem. But there is no reliable data to support the idea that it is rife in the United States or merits emergency action. There is a widespread belief that it does, however, and that has allowed the Trump administration to portray its pitiless war on informal networks of transnational mobility as a way to protect vulnerable people, especially children, from the “criminals” who ply them. And it has helped them justify treating parents seeking physical and economic security for their children as dangerous lawless smugglers of their own sons and daughters.

In his first days in office, the president issued an executive order declaring that “the trafficking and smuggling of human beings by transnational criminal groups risks creating a humanitarian crisis.” The administration has relentlessly characterized the prosecutorial discretion previously exercised to avoid family separation and laws intended to protect detained immigrant children as “loopholes” that have, in Mr. Trump’s words, “created a massive child smuggling trade.”

There is no evidence of “a massive child smuggling trade.” There is no evidence of “humanitarian crisis” involving “transnational criminal groups” apart from the crisis of refugees fleeing civil strife in Central America. When considering the administration’s rhetoric about human trafficking, smuggling rings and the humanitarian benevolence of measures like family separation, which, in the words of John Kelly, the White House chief of staff, deter “movement along this terribly dangerous network,” remember that the Underground Railroad was a dangerous network and criminal human smuggling enterprise.

Homeland Security Secretary Kirstjen Nielsen defended the administration’s family separation policy this week by intimating that there is a torrent of “adults showing up with kids that are not a family unit.” Ms. Nielsen maintains that “those are traffickers, those are smugglers, that is MS-13, those are criminals, those are abusers.”