Joseph was ordered by Caesar to go back to his home town for the census.
So make them go back to Mexico for the 2014 DF census.
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The immigrants are mostly from Central America.
Mexico gives their own citizens brochures with information on how to sneak into the USA.
It's my read that the ONLY way the Central Americans got permission to go through Mexico was the promise of NOT staying in Mexico (TOO many Mexicans living in D.F. already.) and going to the U.S. border.
The Valle de Mexico, the entire city of Mexico and its environs already has 40+ million Mexicans. They want NO poor immigrants from ANYWHERE.