It was supposedly passed to prevent people from impersonating others at the polls, but there is no evidence that this has ever happened in Indiana.
First of all, this assumes that a state should not enact a law aimed at preventing a problem from occurring. Rather, the only role the state legislative function should play is reacting to existing problems. The Editorial also leads one to believe that the law produces an extraordinary and unnecessary burden on voters:
The harm it imposes on voters, some of whom will no doubt be discouraged from casting ballots, is considerable.
But in the Majority Opinion by Justice Stevens, the Court concludes:
on the basis of the record that has been made in this litigation, we cannot conclude that the statute imposes 'excessively burdensome requirements' on any class of voters
I have a hard time believing that requiring a photo identification is a considerable burden. What is the tipping point for what we classify as a "considerable burden"? Voter registration is already required to exercise your right. Is the completion of a voting registration form a considerable burden? There are poor people without the internet and they can't download the application with the simple click of a mouse. That seems like an unequal burden than the rest of us must face. These people also may not live near a Post Office so they can't mail the form back. That too seems unfair.
This is certainly meant to be facetious, but voter registration is already inherently regulated to prevent fraud. Does a photo ID aimed at further preventing fraud present a substantial marginal burden from what needed to be done before. From the concurring opinion written by Justice Scalia:
To vote in person in Indiana, everyone must have and present a photo identification
that can be obtained for free. The State draws no classifications, let alone discriminatory ones, except to establish optional absentee and provisional balloting for certain poor, elderly, and institutionalized voters and for religious objectors....Insofar as our election-regulation cases rest upon the requirements of the Fourteenth Amendment...weighing the burden of a nondiscriminatory voting law upon each voter and concomitantly requiring exceptions for vulnerable voters would effectively turn back decades of equal-protection jurisprudence. A voter complaining about such a law’s effect on him has no valid equal-protection claim because, without proof of discriminatory intent, a generally applicable law with disparate impact is not unconstitutional.
Scalia then properly positioned the standard to be on the individual:
It is for state legislatures to weigh the costs and benefits of possible changes to their election codes, and their judgment must prevail unless it imposes a severe and unjustified overall burden upon the right to vote, or is intended to disadvantage a particular class. Judicial review of their handiwork must apply an objective, uniform standard that will enable them to determine, ex ante, whether the burden they impose is too severe.