ASCS/FSA had a voting register, essentially a subset of the overall name and address file. I never knew how well we maintained it, whether the county offices followed through on their instructions. Basically, they were supposed to, once a year, do a mailing with the request for the postal service to report back any items where the address was wrong. I don't know how well the postal service did this; I'm a bit suspicious of the quality. As far as I know, USPS still has the service though you have to pay a surcharge for the special handling. As far as I know, Ohio doesn't use the approach nor did it become an issue in the litigation. Just skimming the news accounts of the Court's decision it seems the debate was over whether it was rational to assume that a voter who failed to return a postcard had changed her address or was just not responsive to postal reminders.
It seems to me there are two aspects to the voting register: one is whether the register has an accurate mailing address; the other is whether the individual citizen is eligible to vote. And it seems that Ohio and SCOTUS, perhaps many states, are conflating the two, likely because in the old days people didn't move.
Let's start at the beginning:
- a person turns 18 and registers to vote, providing whatever proof of identity and age is currently required by the state, whatever proof of "legal residence" (i.e., tying the citizen to a voting precinct) is required, and the current mailing address. Now in most cases the two addresses will be one and the same, but they needn't be. (Actually, these days the mailing address should be replaced or amplified by email address/smartphone number--it's contact information.)
- Now, the manager of the registry can update the mailing address independently of the legal residence. They can ask the USPS for changes of address, or do as ASCS used to.
- When the person comes into vote, if there's no indication their legal residence has changed (because their mailing address is out-of-date or does not match the residence) they can vote.
- If there is an indication the legal address may have changed, the manager can go through a process to validate the change. IMO logically you'd do an online-verification, ensuring the citizen has only the one legal residence recorded and thus can vote only in one precinct.
- The only reason to drop the citizen from the voting rolls (other than death) would be if the citizenship is revoked or eligibility to vote is lost due to a criminal conviction or declaration of incompetence.
As it stands for Ohio voters dropped from the rolls, they have to go through the process of re-enrolling, like photo-id.