and from the article you linked.
"Whereas President Barack Obama focused on deporting immigrants convicted of serious crimes, new memos signed by Kelly prioritize deportation for anyone convicted of a crime or charged with any offense. That includes crossing the border illegally.
Does this mean that crossing the border illegally hasn't been an offense allowing for deportation? Is it something new and unfair? If I break into a store in the middle of the night, should I be permitted to remain unless I damage or steal something? Or, if I want to live in your house, can I just walk in with my backpack and take up residence...and you can't boot me out unless I do harm to someone or something? I don't see where an illegal border crossing shouldn't be a crime punishable by being sent back.
America is going to send ALL "illegals" to Mexico..even people that aren't Mexican citizens?
Can a country do that?
Does Mexico have to allow them into Mexico?
What can Mexico do to stop them from being forced to cross that border?
Armed guards on both sides of the border...on one side forcing them to cross...and on the other side preventing them from crossing...
Mexican Standoff 2017?
Tillerson and Kelly Visit Mexico In the Wake of Anti-U.S. Protests and a Canceled Summit
"We don't have to, and it is not in the interest of Mexico," Videgaray said. He hinted that Mexico might seek to challenge Trump's move at the United Nations or in other international bodies.
On Tuesday, the U.S. changed immigration enforcement policies that could subject millions of people living in the U.S. illegally — including many Mexicans— to deportation. Whereas President Barack Obama focused on deporting immigrants convicted of serious crimes, new memos signed by Kelly prioritize deportation for anyone convicted of a crime or charged with any offense. That includes crossing the border illegally.
The memos also call for sending some people who enter the U.S. illegally back to Mexico, even if they're from Central America or elsewhere and only used Mexico as a transit point. Detention center capacity will expand; planning for Trump's much touted wall will begin.
What "proof" will be provided to the Mexican Government as to the "belief" that non-citizens of Mexico entered through Mexico?

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