Senator Dianne Feinstein (D-CA) is leading the fight to cripple Attorney General Jeff Sessions’s “zero-tolerance” policy on illegal border-crossers — but she has argued in a previously undisclosed 2014 memo that federal law gives the president broad authority to solve the border problem.

Sessions’s policy of ensuring criminal prosecutions for “improper entry,” including aliens with children, has elicited an outcry from most liberal institutions, including the legacy media, human rights, and special-interest groups, and even the United Nations. This focus by Feinstein and the media on these relatively few children distracts us from recognizing the much larger devastation wrought by U.S. immigration policy on Mexico and Central America.

In his book, A Nation of Emigrants, migration scholar David Fitzgerald writes that the mass exodus of Mexicans has led massive family separation back home.

As much as 20 percent of Mexico’s middle-west region of Los Altos had picked up and left for the United States, according to a survey conducted after the 1986 congressional amnesty.

The survey found that a full 75 percent of residents had at least one family member who had gone, and of those families, 20 percent had included married couples who had permanently separated as a result. According to Fitzgerald, such mass dislocation had further led to five percent of married couples divorcing “usually because an emigrant man had abandoned the family.”

Mexico-based journalist Robert Jay Stout shows that a full 12 percent of Mexico’s adult population is now in the United States, according to 2010 census numbers. Such mass outmigration, he found, has contributed to 40 percent of Mexico’s rural towns and villages suffering a population loss as high as 70 percent. Whole communities were uprooted.

The ongoing exodus has resulted in a dramatic increase in the number of single-parent families, homeless, and runaway children — allowing gang membership to proliferate, he says.

David Fitzgerald concurs. In interviews with school administrators across the border, he writes that absenteeism-rates are especially high among children of fathers who’ve left for the United States. As one school official told him, “It’s more difficult to control adolescents when only the mother is there, and there are a lot of problem kids in the school … I think many of the problems have to do with this (migration).”

There are additional consequences. An estimated 30 percent of Mexico’s scientific and engineering grads and 10 percent of its university-educated population in general, were living abroad (the U.S. mostly) in 1990; figures which had increased by 2000.

The United Nations, the International Monetary Fund, and the Organization for the Americas have all found similar debilitating rates for the rest of the region.

The latter cited El Salvador as the worst hit, noting that “one out of every five Salvadorans currently lives outside of the country [which has] provoked a parallel exhaustion of qualified human resources.” This, they say, had caused “a scenario in which less than 11 percent of Salvadorans [have] tertiary education.” Draining an already underdeveloped nation of its best and brightest reduces any prospect of establishing a knowledge-based economy, and disincentivizes their political elite from investing in sorely needed educational infrastructure.

This damage adds up to intellectual colonialism, in which the superpower to the north plunders and loots the skilled labor from its poorer neighbors and condemns them to a bleak future.

As those countries continue to struggle with debt, poverty, and hopelessness 30 years from now, how will America be judged for its role in creating that situation?

Who is truly separating the most families? Those who champion lax immigration standards or those who implement clear and consistent enforcement?

Yale psychologist Paul Bloom, an expert in the study of human empathy, says that, too often in the policy field, we focus our attention on individual cases, which causes us to lose sight of larger tragedies. Empathy’s “spotlight nature,” he writes, “renders it innumerate and myopic,” disallowing people to see the “effects of our actions on groups of people.”

The reaction against Sessions over zero tolerance should be a textbook case for Professor Bloom. Anecdotal accounts of parent-child separations make it difficult for people to see the greater tragedy: The damage that our loose immigration system carelessly inflicts on whole groups of people and nations.

We know Feinstein once recognized the damage caused by loose borders — and that the President already has the legal authority to fix the problem.

Back in 2014, when the surge of the unaccompanied alien children (UAC) and “family-units” was at a height, Senator Feinstein penned a private memo to then-President Barack Obama urging stronger border enforcement

The Immigration Reform Law Institute got a copy of the memo via FOIA, and it shows that Feinstein knows existing law allows the President to solve many border problems without action by Congress.

Feinstein showed how the President has the authority to set broad suspension-of-entry power in 8 USC §1182(f). The authority allows the President to do far more than he is doing now: Place all UACs in DHS detention facilities, drop the standards at those facilities to maximize occupancy, and limit UACs’ rights to appeal their removal orders.

Less emboldened now than she was back in 2014 (she does have a tough re-election coming up), if family separation is truly a concern for Feinstein, she and her supporters must revive her 2014 legal recommendations — and so help migrants and their own nations.

Dale L. Wilcox is executive director and general counsel at the Immigration Reform Law Institute, a public interest law firm working to defend the rights and interests of the American people from the negative effects of mass migration.