The U.S. Supreme Court refused to say whether states and cities can bar landlords from renting to undocumented aliens. The justices turned away a challenge to a Nebraska law that civil rights advocates said conflicts with federal immigration measures. A St. Louis-based federal appeals court upheld the law, putting it at odds with appellate courts that have considered similar measures elsewhere. The Supreme Court previously put limits on what states and local governments can do to crack down on illegal immigration. Since then, the Supreme Court has repeatedly sidestepped the issue of anti-harboring laws.