The Justice Department says the Alabama law conflicts with federal law and undermines federal immigration priorities.
In a lawsuit filed in federal court in Alabama, the government says the state law expands the opportunities for Alabama police to push immigrants toward incarceration for various new immigration crimes.
The Justice Department says a state cannot set its own immigration policy and cannot pass laws that conflict with federal immigration laws.
The department quoted Birmingham police chief A.C. Roper as saying the law would divert scarce resources from local priorities to immigration enforcement.
Last year, the department obtained a preliminary injunction against an Arizona immigration law.