Trump is declaring a national border emergency and taking others steps to curb immigration. Here's what that means.

Newly sworn-in U.S. President Donald Trump said on Monday that he would declare illegal immigration a national emergency, send troops to the U.S.-Mexico border, and reinstate his "remain in Mexico" policy as part of a sweeping immigration crackdown.

Trump pledged to declare a national emergency at the country’s southern border and “begin the process of returning millions of criminal aliens” to their home countries. The president said he would reinstate the “Remain in Mexico” program that began under his first administration.