As my previous posts have demonstrated, I am a big fan of Slate and of the Explainer column, but their column on Mexican immigration laws entirely misses the point. The Slate column focuses on Mexico's immigration laws, pondering whether they are tougher than American ones. But the prompt for this piece is not US immigration law but Arizona's blast to Germany's and South Africa's pasts: "I need to see your papers!"
So, the question really is not whether Mexico has tougher laws than the US (yes, in some ways) but rather do Mexican states, such as Chihuahua or Durango or Chiapas have their own immigration procedures, policies and enforcement? I don't know. I doubt it. However, one province in Canada has its own immigration policies and apparatus: Quebec. American federalism is symmetric--all states have the same powers and responsibilities (more or less), but in Canada, one province tends to have more authority over more issues. I had to make it through the Quebec immigration process before Canada would consider my immigration file. So, if one wants to ponder about Arizona, focusing on Mexico, ironically, may be in the wrong direction.