Not every law that’s constitutional is also wise. Keep that in mind as you read the Supreme Court‘s ruling on the 1965 Voting Rights Act.

It seemed like an easy case. How could a federal statute designed to end the historic suppression of African American voting not be constitutional? The 15th Amendment gives voters of all races equal rights and expressly grants Congress the power to enforce those rights — which Congress exercised by reauthorizing the Voting Rights Act (VRA) for 25 years in 2006.

The vote was 98 to 0 in the Senate and 390 to 33 in the House; a conservative Republican president from Texas, George W. Bush, signed the legislation.

If judicial restraint means anything, surely it counseled Supreme Court affirmation of the VRA against the challenge by Shelby County, Ala., which says that because it has basically ended voter discrimination Congress has no right to subject it, or other mostly Southern jurisdictions, to Justice Department “pre-clearance” of its election rules, as prescribed in Section 5 of the law.

As Judge David Tatel of the U.S. Court of Appeals for the D.C. Circuit wrote for the majority of a three-judge panel last year, “in this context, we owe much deference to the considered judgment of the People’s elected representatives.”

Here’s the problem: Although hugely successful at securing the franchise for individual black voters, the Voting Rights Act has had corrosive unintended consequences, including, ironically, greater political polarization along racial lines.

As construed by courts, modified by Congress and enforced by the Justice Department, the act all but requires covered jurisdictions to maximize the concentration of African American and other minority voters in legislative districts.

In theory, this enables minorities to elect candidates “of their choice.” In practice, it divides many states into a small number of majority-black districts, which usually pick liberal African American Democrats, and a larger number of overwhelmingly white districts, which choose conservative white Republicans. Moderates get squeezed out.

The Voting Rights Act is one reason House debates so often pit upstart tea party Republicans from Southern suburbs against veteran African American Democrats from Southern cities.

Civil rights organizations defended the legislation’s current incarnation as if the risks to minority enfranchisement were unchanged since 1965. This is understandable. Much as affirmative action in universities helped build a middle class after segregation, “opportunity districts” for minority candidates helped create a cadre of black elected officials. The act’s pre-clearance showed continuing relevance as a check on potentially discriminatory voter ID laws in Texas and South Carolina.

Still, the law too often produced anomalies such as the 2003 case Georgia v. Ashcroft, in which civil rights organizations sided with a Republican Justice Department against a state redistricting plan on the grounds that it did not create enough majority-minority districts — even though Georgia’s African American Democratic officeholders overwhelmingly supported the plan because they wanted to spread black votes, and influence, more widely.

For the most part, minority voters no longer face the kind of blunt denial of voting rights that gave rise to the 1965 act; in 2012, blacks voted at a higher rate than whites, according to a Pew Research Center analysis .

Ann Telnaes animation: Justice Antonin Scalia says renewing the Voting Rights Act is a "perpetuation of racial entitlement." (Ann Telnaes/The Washington Post)

In such a world, the corrosive political effects of racial gerrymandering under the VRA loom larger — even compared with the benefits to minority candidates. The creation of safe minority districts put a floor under the number of blacks elected but also, arguably, a ceiling over how high they can rise.

In the South, the message and ideology that win in a majority-minority district rarely work at the (majority-white) statewide level.

Congress didn’t really tackle such issues when it extended the Voting Rights Act in 2006. Small wonder: Incumbents of both parties and all races owe their positions to the current system. A shake-up of the status quo might have exposed them, and then-President Bush, to election-year charges of racial insensitivity.

Fact is, Tuesday’s decision by the Supreme Court was eminently foreseeable. By 2006 the court had expressed concerns about the real-world consequences of the Voting Rights Act in several cases, and it has again since then.

It was no surprise that the Roberts Court gutted the statute’s pre-clearance provision — holding that rules based on mid-1960s political realities are simply out of sync with the 21st century.

It was a pretty activist ruling. But it might just start a healthy debate about how we can protect voting rights while restoring the nation’s political center.

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