Suddenly the left doesn't think Sen. Rand Paul of Kentucky is so crazy after all.

A week after U.S. Attorney General Eric Holder made a strong case for restoring voting rights to felons, the Kentucky Senate joined the Kentucky House in approving a constitutional amendment restoring rights to many felons, and Paul prefers the broader version passed by the Democratic-controlled House.

Voting rights for felons is an issue of convergence for liberals and libertarians. But it invites another question: What about gun rights?

That is, if citizens who have paid their debt to society should regain their constitutional right to vote, as Holder argued, why should they not regain their constitutional right to own a gun as well?

It's a question Paul and other conservatives — not to mention the National Rifle Association — increasingly will be asking.

Federal law prohibits all felons from possessing guns, but states may restore felons' gun rights after restoring their civil rights — the right to vote, sit on juries and hold office. In 11 states this happens automatically for non-violent felons, and some states even allow violent felons to recover their gun rights. In most states, however, all felons must petition to have their gun rights restored. In Kentucky, only a pardon from the governor can restore gun rights, and the same is true for voting rights.

Holder's case for restoring voting rights to felons rests partly on race. The numbers are indeed unsettling: Across the country, one of every 13 black citizens is barred from voting. In Florida, Kentucky and Virginia, the number is one of every five. Those disparities also hold true for citizens denied the right to own a gun.

If laws disproportionately deny black citizens a constitutional right, isn't that wrong, no matter what the right? Holder played into this argument, but the issue isn't so black and white.

The Supreme Court has granted states substantial leeway to restrict both voting and gun rights based on criminal behavior. The key question is: What purpose is served by doing so?

Disenfranchising felons doesn't serve as a deterrent to would-be criminals. It's hard to picture a group of bank robbers worrying about whether they'll be able to vote in the next congressional election before donning ski masks. Nor does it aid in their rehabilitation; if anything, it further ostracizes them from society.

It does, however, allow society to prevent citizens who have broken laws from participating in decisions about what those laws should be. And that, the argument goes, protects society. But what risk does society actually run by allowing ex — cons to vote? Based on the experience of states that have done so, none.

Now turn that same question to gun rights: What risk does society run by allowing ex-cons to possess guns? Based on the evidence, a substantial risk. Felons re-offend at a high rate. Allowing them to do so with a gun in their hands puts society in grave danger. And there are many instances — some documented in a 2011 New York Times expose — of felons who committed violent crimes after having their gun rights restored.

A blanket restoration of felons' gun rights would pose a real danger to society. Not so with voting rights. Nevertheless, any blanket ban on the exercise of rights is bound to create injustices, and just as some states have made it too easy for violent felons to recover their gun rights, some states have made it too hard for non-violent offenders to recover theirs. A strong case can be made that those who pose the least risk to society — perhaps non-violent first offenders with no drug convictions — should have their gun rights restored after they have served their time and completed their probation or a minimum waiting period with no re-arrests.

Congress could ensure that states are not unduly depriving people of their gun rights by requiring them to restore rights in certain narrow categories of cases. And maybe — just maybe — that idea could create an opening for new bipartisan legislation that would, while restoring gun rights to a significant number of people, close loopholes in the background — check system that would keep guns out of the hands of the truly dangerous.