Voter caging involves challenging the registration status of voters and calling into question the legality of allowing them to vote. Usually it involves sending mail directly to registered voters and compiling a list from mail returned undelivered. Undeliverable mail is seen as proof that the person no longer resides at the address on their voter registration. The resultant list is then used by election officials to purge names from the voter registration rolls or to challenge voters' eligibility to vote on the grounds that the voters no longer reside at their registered addresses. In the United States, the practice of purging voter rolls has been challenged by the American Civil Liberties Union, Fair Fight Action, and other voting rights advocates in the courts for perceived racial bias when minority neighborhoods are targeted, and some courts have declared such purging illegal under the Voting Rights Act of 1965. However, the practice remains legal in many states, and the U.S. Supreme Court rejected a 2018 legal challenge to Ohio's list-maintenance process. Method Voter caging typically refers to the practice of sending mail to addresses on the voter rolls, compiling a list of the mail that is returned undelivered, and using that list to purge or challenge voters' registrations and votes on the grounds that the voters on the roll do not legally reside at their registered addresses. Usually, a political party will send out non-forwardable, first-class mail to voters or particular voters they want to target (often assumed to be a demographic that belongs to the opposing party). It will compile a list of voters for whom mail has been returned as undeliverable. The list is called a caging list. In some cases, such mail can be returned at a rate of 1 in every 15 letters sent out, as shown in Ohio in 2008 when the Board of Elections had 600,000 letters of voter confirmation returned as undeliverable. The party uses caging lists created by themselves or by the Board of Elections to challenge the registration status of voters and potentially purge them from the voting rolls under state laws that allow voters whose registrations are suspect to be challenged. When voters turn out to vote, they may be challenged and required to cast a provisional ballot. If investigation of the provisional ballot demonstrates that the voter has just moved or there is an error in the address and the voter