The Supreme Court is scheduled to hear oral arguments Wednesday in a case that challenges Ohio's policy of dropping infrequent voters from its registration rolls.
Under the rule, Ohio residents who fail to vote in two consecutive elections and don't return a mailed confirmation form are removed from the registration rolls.
Critics argue the rule violates federal law and voters' rights. But the state says it helps keep voter registration lists up-to-date.
The court's ruling is expected in late June.