From this:

In the legal battle over Arizona's new immigration law, an ironic subtext has emerged: whether a Bush-era legal opinion complicates a potential Obama administration lawsuit against Arizona.

The document, written in 2002 by the Justice Department's Office of Legal Counsel, concluded that state police officers have "inherent power" to arrest undocumented immigrants for violating federal law. It was issued by Jay S. Bybee, who also helped write controversial memos from the same era that sanctioned harsh interrogation of terrorism suspects.

The author of the Arizona law -- which has drawn strong opposition from top Obama administration officials -- has cited the authority granted in the 2002 memo as a basis for the legislation. The Obama administration has not withdrawn the memo, and some backers of the Arizona law said Monday that because it remains in place, a Justice Department lawsuit against Arizona would be awkward at best.