A federal appeals court on Friday rejected the demands by Arizona and Kansas that federal forms for voter registration used in their states require documentary proof of citizenship.

The decision, by the United States Court of Appeals for the 10th Circuit, in Denver, is the latest step in years of legal conflict between the states and the federal Election Assistance Commission over who has ultimate power over voting procedures.

Most experts say there is no evidence that significant numbers of noncitizens have registered, an act that could lead to their arrest and deportation. But the issue has become embroiled in the emotional politics of immigration.