Attorneys with the U.S. Department of Justice yesterday filed suit to block an Alabama law that's been called the harshest attempt at an immigration crackdown anywhere in the nation.

Alabama's law, which was signed by Gov. Robert Bentley (R) in June, would have illegal immigrants jailed until their immigration status could be verified. A charge of trespassing would be filed if anyone suspected of being undocumented were found out. It would also criminalize anyone who knowingly transports an illegal immigrant, and require employers to use an e-verify system to ensure their workers are citizens.

And much like the most controversial proposal from Arizona's immigration battle, it would empower police to investigate immigration status based upon "reasonable suspicion," which opponents say effectively enshrines racial profiling into law.

“Today’s action makes clear that setting immigration policy and enforcing immigration laws is a national responsibility that cannot be addressed through a patchwork of state immigration laws,” Attorney General Eric Holder said in a media advisory.

"The department is committed to evaluating each state immigration law and making decisions based on the facts and the law. To the extent we find state laws that interfere with the federal government’s enforcement of immigration law, we are prepared to bring suit, as we did in Arizona."

The law was also challenged by a coalition of immigration advocacy groups led by the American Civil Liberties Union, in a suit (PDF) that alleges the law violates the Fourth Amendment's protections against unreasonable search and seizure.