Civil rights and immigrant rights groups filed a lawsuit on Thursday alleging that Iowa's new law making it a crime to be in the state if previously denied admission to the U.S. is unconstitutional. It’s the first legal action taken against Iowa in response to the law, though the U.S. Department of Justice warned the state's top officials last week that the agency would sue unless they agreed not to enforce it. The complaint filed Thursday alleges that the new statute steps on the federal government’s authority to enforce immigration law.