Clearly the federal government has not stopped the 'invasion' in Arizona, nor have they enforced the existing laws....so Arizona is going to do it themselves!
Article IV section 4- The United States shall guarantee to every state in this union a republican form of government; & shall protect each of them against invasion; & on application of legislature,.......
In this case, the state can do as it pleases..........
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.