In gutting the Voting Rights Act, the U.S. Supreme Court's conservative justices have once again superseded the will of the Congress, ignoring precedent in the process and constructing a frail constitutional framework to justify their ruling.

Passage of the Voting Rights Act in 1965 was among the greatest achievements of the civil rights movement that ended institutional discrimination in the South. The act's intent was to enforce the dictates of the Fifteenth Amendment, ratified after the Civil War: "The right of the citizens of the United States to vote shall not be denied or abridged by the United States or any State on account of race, color, or previous condition of servitude."

Section 2 of the Amendment makes it clear that "Congress shall have the power to enforce this article by appropriate legislation."

Congress has used that constitutional authority to extend the 1965 Voting Rights Act several times and the high court has repeatedly upheld its constitutionality. Congress most recently renewed the act for 25 years in 2006 after extensive hearings, the vote 390-33 in the House and unanimous in the Senate.

Congress concluded then "40 years has not been a sufficient amount of time to eliminate the vestiges of discrimination following nearly 100 years of disregard for the dictates of the 15th Amendment and to ensure that the right of all citizens to vote is protected as guaranteed by the Constitution."

But in a 5-4 decision written by Chief Justice John G. Roberts Jr., and joined by justices Antonin Scalia, Anthony M. Kennedy, Clarence Thomas and Samuel A. Alito Jr., the conservative wing of the court concluded that it did not like the formula Congress uses to judge which states and jurisdictions needed closer monitoring to protect voter rights.

Section 4 of the Voting Rights Act outlines the nine states in the South and Southwest (and numerous other voting districts scattered around the country) that are subject to Section 5's "preclearance" requirement. These states and jurisdictions must obtain permission from the Justice Department before amending voting laws and regulations, assuring those changes are not discriminatory.

Congress has not updated Section 4 since 1975. The court's majority concluded that is too long. If Congress requires some states and jurisdictions to receive preclearance, it must base that requirement on contemporary data; otherwise it is a violation of state rights, the majority concluded.

"The (Fifteenth) Amendment is not designed to punish for the past," Chief Justice Roberts writes. "Its purpose is to ensure a better future."

The majority argument finding Section 4 unconstitutional is fundamentally flawed. How to ensure a better future, what formula to use, whether it should be changed and to which states it applies are decisions for Congress to make, not the Supreme Court. The Fifteenth Amendment could not be clearer on that point. Writing the opinion of the four dissenting justices, Ruth Bader Ginsburg put it well.

"The body (Congress) empowered to enforce the Civil War Amendments 'by appropriate legislation' merits the Court's utmost respect. In my judgment, the Court errs egregiously by overriding Congress' decision," writes Justice Ginsburg.

During oral arguments last March about the case - Shelby County, Ala. v Attorney General Holder - Justice Scalia signaled the conservative court's direction. "This is not the kind of a question you can leave to Congress," said the justice about his concern Congress would never modify the Voting Rights Act. Gee, that sounds like judicial activism.

Theoretically, Congress could, in an effort to pass constitutional muster, rewrite Section 4 with a new formula based on new data. Given the current climate in Congress, reaching agreement on new federal guidelines is probably impossible.

This misguided decision presents a genuine threat to voting rights. In the past two years the attorney general has used the act to block state voter identification laws that would have adversely affected minority voters.

Due largely to the act, the country has made tremendous progress in reducing voter discrimination, but it is naïve to think that when politicians in these states see it in their interest to repress the votes of the minority community they won't try again. Now, they won't have a functioning Voting Rights Act to stop them.