MEXICO CITY- Mexico’s newly created National Guard has detained U.S.-bound migrants and the government should make public the rules governing their power to curb immigration, the head of the government’s human rights ombudsman said on Monday.

The National Guard is a security force created by Mexican President Andres Manuel Lopez Obrador to bring down record homicide rates. But now it has been tasked with patrolling the border to placate U.S. President Donald Trump, who threatened to slap tariffs on Mexican imports unless the country did more to stem the flow of Central American migrants heading to the United States.

“Publishing the protocols and coordination rules under which the National Guard operates in support of immigration authorities, particularly regarding the procedures for detaining persons with an illegal immigration status, is desirable,” Luis Raul Gonzalez, president of the National Human Rights Commission (CNDH), said in a speech. “If such protocols and rules don’t exist, establishing and publishing them is an urgent matter.”

The Mexican government did not immediately respond to a request for comment on the speech.

While some 21,000 National Guard troops, nearly a third of their total ranks, have been deployed to Mexico’s northern and southern borders on immigration duties, their rules of engagement are still unclear.

“It’s necessary for the National Guard to operate within an adequate regulatory framework that gives certainty to its members, to society, encourages the proper development of its functions and curbs human rights violations,” Gonzalez said.

Facing accusations the troops had been heavy-handed in their efforts to deter migrants from crossing the northern border, Lopez Obrador said on June 25 that the National Guard does not have orders to detain migrants.

The guardsmen themselves say they do not detain migrants but are there to advise them not to enter the United States.

Still, Reuters witnessed at least three adults and four children being detained as they tried to cross into the United States after Lopez Obrador made his statement.

Last week, Brigadier-General Vicente Antonio Hernandez, who heads the National Guard’s operations in Mexico’s southern states, said 20,000 migrants had been “rescued” since May 17. Human rights groups say the migrants have been detained and some have been deported.

“There is a huge distance between what you hear from Lopez Obrador every morning and what is happening on the ground with respect to this issue,” Fernando Garcia, founding director of the Border Network for Human Rights, told Reuters. “He’s not being very truthful, not being very honest with Mexican people regarding the reality of the deployment of these soldiers.”

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