US News reports on a little remembered law passed by Congress in 1996:

Back in 1996 (when fanny packs were still cool, in some circles) it was time to get tough on immigration, and an interesting little law was passed. Congress deemed it appropriate for state and local law enforcement to enforce immigration law. In the inscrutable manners of Washington (where all legislation seems to be named with insufferably cute acronyms or indecipherable legislative codes that read like security passwords), this law came to be known as 287g.

Want to know what 287g says? Well, just read the law in Arizona. Yes, that law. The one causing protests in the streets of Phoenix, hysteria on cable talk shows and confusion in the courts. The one that empowers state and local law enforcement to enforce immigration law.

The only reason Arizona currently runs afoul of this law is that the law also provided for the Department of Homeland Security and ICE to approve of the state enforcement and provide training.

So instead of suing Arizona, why didn't President Obama encourage DHS and ICE to train Arizona officials?