From my understanding, Arizona cannot sucede from the U.S. legally. What they can do is attempt it and it may wake up the rest of the states in a big way. As well as the people.
If a state were to secede, the Federal governments legal system really wouldn’t matter anymore. What are they gonna do, sue them in the World Court? Would that matter if they didn’t recognize them as well?
The actually is one way. The states could call for a Constitutional Convention, then pass an amendment allowing for secession.
Other than that, impossible. As someone once wrote, the Civil War made it "settled law" that states cannot secede from the Union as the Constitution stands now.
And for what it's worth, I'd love to see the states at least talk about calling for a Convention. Maybe that would scare the Fed's into respecting the 10th amendment.
Section. 4. The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.
In 1776 it was also illegal for the 13 colonies to secede from Great Briton. Then in 1861, 11 states did and it cost 600,000 lives to "Save the Union". I would guess that if Arizona did atempt to secede, there would be hell to pay. Both in the courts and in the field. That said, I would be more than happy to live in the Republic of Arizona.