Officially, the Constitution of the United States gives everyone on U.S. soil equal protection under the law – regardless of nationality or legal status.

But, as recent stories of the neglectful treatment of migrant children in government detention centers demonstrate, these civil rights are not always granted to immigrants.

We are scholars focused on U.S.-Mexico migration. Our report on the enforcement of U.S. immigration law under presidents Barack Obama and Donald Trump, presented in February to Mexico’s National Human Rights Commission, documented pervasive and systematic civil rights violations against Mexicans living in the United States.

Some of the abuses we documented – which include racial profiling, discriminatory treatment and due process violations – result from the Trump administration’s anti-immigration policies. Others began much earlier, under Obama or well before.

All paint a troubling picture about the rule of law in the United States and the challenges facing America’s largest immigrant group.

Discrimination and deportation

An estimated 11.3 million people born in Mexico now live in the United States – 3% of the total U.S. population.

About 5 million of them are unauthorized immigrants, meaning Mexicans make up just under half of the 10.5 million undocumented immigrants in the country. The other 6.3 million Mexicans in the U.S. are either lawful permanent residents or dual nationals who are naturalized U.S. citizens.

Based on these figures, we found, Immigration and Customs Enforcement – or ICE, the agency that carries out the nation’s immigration laws – arrests Mexican immigrants at levels that are disproportionate to their share of the unauthorized immigrant population.

Roughly 70% of immigrants deported from the U.S. interior in 2015 were Mexican, the most recent year that such detailed deportation data are available.

Another 550,000 young Mexican American “Dreamers” – immigrants who were brought to the U.S. unlawfully as children – became subject to deportation when Trump in September 2017 rescinded the Deferred Action for Childhood Arrivals program, which gave them temporary protection from deportation.

Not all deportations violate immigrants’ civil rights. The Immigration and Nationality Act says immigrants may be deported for violating a long list of criminal and administrative laws.

But evidence suggests that Mexicans and other Latinos are sometimes targeted for arrest based on their race or ethnicity.

In 2014, independent monitors at a Customs and Border Protection checkpoint in Arivaca, Arizona, just north of the U.S.-Mexico border, found that vehicle occupants who appeared to be Latino were 26 times more likely to be asked to show identification than white-looking vehicle occupants, who are frequently waved through the checkpoint.

And in 2012, a U.S. Department of Justice investigation in Alamance County, North Carolina, found that the sheriff had instructed deputies to “go out there and get me some of those taco eaters” by targeting Latinos in traffic stops and other law enforcement activities.

The DOJ concluded that the county demonstrated an “egregious pattern of racial profiling” – a violation of the 14th Amendment, which guarantees everyone equal protection under the law.

Family separation

Mexicans in the United States have seen their constitutional rights violated in other ways.

The most egregious example was the forced separation of families found to have crossed the border illegally.

Under this Trump administration policy, which began in April 2018, at least 2,654 migrant children – and perhaps thousands more – were taken from their parents and held in government custody while their parents were criminally prosecuted for crossing the border unlawfully.

Thirty of the children known to have been separated from their families were Mexican; the rest were from Central America. Poor record-keeping has made it difficult for all of them to be reunited with their families before their parents’ deportation.

Together, these actions violate the constitutional rights to legal due process, equal protection and, according to the Southern District of California, the right of parents to determine the care for their children.

“The liberty interest identified in the Fifth Amendment provides a right to family integrity or to familial association,” wrote Judge Dana M. Sabraw in a June 2018 ruling.

More routine civil rights violations happen to Mexicans in the U.S. every day, our report found.

Though children born in the U.S. are entitled by law to American citizenship regardless of their parents’ immigration status, hundreds of undocumented Mexican women in Texas have been denied birth certificates for their U.S.-born children since 2013, according to a lawsuit filed by parents. In 2016, Texas settled the lawsuit and agreed to expand the types of documents immigrants can use to prove their identity.

And in both Arizona and Texas, so-called “show me your papers” laws allow police to demand identification from anyone they have a “reasonable suspicion” may be undocumented, which may lead to discriminatory targeting of Latinos.

Once in government detention, surveys conducted in Mexico of recently deported immigrants show, Mexican deportees are often badly treated.

On average, in 2016 and 2017, about half of all recently deported Mexicans reported having no access to medical services or a bathroom while in government custody. One-third reported experiencing extreme heat or cold.

Mexicans are not alone in their negative experiences at border patrol facilities.

A recent report by the Office of Inspector General found unsafe and unsanitary conditions at several U.S. immigrant detention centers, and immigration lawyers found food shortages at some migrant children’s shelters.

A climate of fear

While Mexicans in the United States have faced biased law enforcement and discrimination for many decades, their treatment appears to have worsened since President Trump took office in 2017 with an openly anti-Mexican agenda.

A survey of Mexicans recently deported from the United States found that the number of people who reported experiencing verbal abuse or physical assault during their time in the U.S. increased 47% between 2016 and 2017.

The number of hate crimes against Latinos reported to the FBI also rose 24% in 2017 compared to 2016 – increasing from 344 incidents to 427.

Mexico is concerned about its citizens in the United States.

In March, President Andrés Manuel López Obrador and foreign minister Marcelo Ebrard announced it would provide more consular services online to increase the reach of Mexico’s 50 brick-and-mortar consulates in the U.S. and provide more legal training to consulate officials.

To support Mexicans in the U.S. with deportation and other immigration cases, the Mexican government will also strengthen its official ties with U.S.-based legal aid providers.

In theory, Mexico shouldn’t have to scramble to defend the rights of its citizens in the U.S. because the U.S. Constitution would. But, in practice, the civil rights of immigrants are simply not always guaranteed.

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David FitzGerald has received research funding from Mexico's National Human Rights Commission.

Angela Y. McClean and Gustavo López do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.