2010 was the beginning of one of the controversial law named unconstitutional by different groups and also claimed by the current US President. The SB 1070, followed by the HB 56 from Alabama 2011, is meant to control the illegal immigration in Arizona. Both acts were supposed to clean streets from criminals. The procedure to do such control is summarized as if someone is asked by their documents and s/he is not carrying them, then that person can be detained.
It sounds like depending on how you look, they can prosecute you and detain you, without chance to come home to take your documents.
This act has been under debate, and protests against it took place around the US. Finally, the last step to be applied, before the law goes into effect, happens next april 25 2012 in Washington. Allegations on this act are going to be presented at the US Supreme Court, which shall decide the consitutionality of the law and therefore whether it can go into effect or is the Governament having such constitutional
The immigration issue is very sensitive in the current world and US financial crisis. There is no loger chance to reach the "American dream". It seems that now the dream is not being prosecuted, arrested and condemned with the only administrative charge of coming to the US to reach such dream.
Here there is a good summary on the steps followed by the SB 1070.