Why isn't Obama's administration suing sanctuary cities?

Why isn't Obama's administration suing sanctuary cities?
By: Peyton R. Miller
Weekly Standard
06/23/10 12:21 PM EDT

The Justice Department is preparing a lawsuit against Arizona’s controversial immigration law, likely to be filed next week. Secretary of State Hillary Clinton told a South American interviewer last week that the Obama administration opposes the law because “the federal government should be determining immigration policy.â€