I think this is a bad ruling.... If people registered, they should not be denied the right to vote, just because the y missed a couple of elections.
This doesn't deny people the right to vote just because they missed a couple of elections. It simply cancels the registration of individuals who don't vote at all for six years (which includes three Congressional elections, two Senatorial elections, one or two gubernatorial elections, and one or two presidential elections, plus the associated primaries for all those), AND who don't respond to a mailing with a pre-paid return card. If, for some reason, someone doesn't vote for six years, doesn't return the card, and then wants to start voting again, so they have to do is register, which can be done at about a bajillion locations (any BMV location, public library, public high school, etc.) or even online.
This doesn't punish anyone or deny the right to vote, it just helps the state ensure that people don't stay on the vote rolls indefinitely after moving. This procedure was established by a Democrat Secretary of State, and continued by a Republican, so it's clearly not intended as a partisan action to favor one party over the other.
Yet another nail in the coffin of what used to be America.