USDoJ Sues Arizona:  AP writer Bob Christie reports that the federal government filed a lawsuit against portions of Arizona's recently enacted illegal immigration law today.  The suit, which was filed in the Federal District Court in Phoenix, claims that the Arizona law will "cause the detention and harassment of authorized visitors, immigrants and citizens who do not have or carry identification documents."  The suit argues that the Supremacy Clause gives the federal government exclusive authority to enact and enforce laws against illegal immigration. A copy of the federal complaint is here.  Noting that the ACLU and other groups have already filed suits challenging the law, law professor Kris Kobach, who helped draft it, called the government's suit "unnecessary."  "The issue was already teed up in the courts.....the Justice Department doesn't add anything by bringing their own lawsuit," he added.