Voter rights were back on the agenda Monday at the Supreme Court as the nation’s top court took up a controversial law that requires stringent proof of citizenship for voter registration. At issue is an Arizona law that aims to block illegal immigrants from casting ballots by demanding proof well beyond what is required under federal law of those seeking to inscribe their names on voter lists. The latest legal bout comes just weeks after the Supreme Court heard arguments over — and appeared poised to overturn, at least in part — the 1965 Voting Rights Act, which requires nine mainly southern states and local governments in seven other states to obtain Justice Department approval for any changes in their electoral codes.