So reports the Republic this afternoon, citing “sources”:

Top Justice Department officials have drafted a legal challenge that could be filed in federal court in Arizona asserting that the state’s new immigration law is unconstitutional because it impinges on the federal government’s inherent authority to police the nation’s Southwest border with Mexico, sources said Wednesday.

At the same time, the government officials said, the department’s civil rights division is considering possible legal action against the law on the basis that it amounts to racial profiling of Latinos who are legally in Arizona but conceivably could be asked to provide documents proving their citizenship.

The story says U.S. Attorney General Eric Holder met with ten police chiefs who oppose the law—the story doesn’t say whether any were from Arizona—and says he told them his department would take action “soon.”