Race discrimination in election practices is hardly a thing of the past, and it is imperative that the U.S. Supreme Court uphold the constitutionality of Section 5 of the Voting Rights Act when it decides Shelby County, Alabama v. Holder, to be argued on February 27.

It always is tempting to declare that our society is post-racial and that racism is over. In 1883, less than two decades after the Civil War, the Supreme Court in the Civil Rights Cases declared unconstitutional the Civil Rights Act of 1875 and said that "[w]hen a man has emerged from slavery, and by the aid of beneficent legislation has shaken off the inseparable concomitants of that state, there must be some stage in the progress of his elevation when he takes the rank of a mere citizen and ceases to be the special favorite of the laws."

Now challengers to Section 5 of the Voting Rights Act are arguing that the law is no longer needed because race discrimination in voting is largely a thing of the past. That is simply wrong, and the Supreme Court should defer to the nearly unanimous judgment of Congress that this law remains an essential weapon in the fight against race discrimination in voting.

The Voting Rights Act of 1965 is one of the most important civil rights laws in American history. Section 2 of the act prohibits voting practices or procedures that discriminate on the basis of race or against certain language minority groups. Under the 1982 amendments to Section 2, the act is violated by state or local laws that have the effect of disadvantaging minority voters. Lawsuits can be brought to challenge state or local actions that are alleged to violate Section 2.

But Congress, in adopting the Voting Rights Act, concluded that allowing lawsuits to challenge election procedures was not adequate to stop discrimination in voting. Lawsuits are expensive and litigation is often lengthy. Congress was aware that especially Southern states often invented new ways of disenfranchising minority voters. Section 5 of the Voting Rights Act was adopted to prevent such actions.

Section 5 applies to jurisdictions with a history of race discrimination in voting and requires that there be preapproval — termed "preclearance" — of any attempt to change "any voting qualification or prerequisite to voting, or standard, practice, or procedure with respect to voting" in any "covered jurisdiction." The preapproval must come either from the attorney general of the United States, through an administrative procedure in the Department of Justice, or from a three-judge federal court in the District of Columbia through a request for a declaratory judgment.

In South Carolina v. Katzenbach (1966), the Supreme Court upheld the constitutionality of Section 5 of the Voting Rights Act and spoke of the "blight of racial discrimination in voting." Congress repeatedly has extended Section 5, including for five years in 1970, for seven years in 1975, and for 25 years in 1982. After each reauthorization, the court again upheld the constitutionality of Section 5. Georgia v. U.S. (1973); City of Rome v. U.S. (1980); Lopez v. Monterey County (1999).

In 2006, Congress voted overwhelmingly — 98-0 in the Senate and 390-33 in the House — to extend Section 5 for another 25 years and President George W. Bush signed this into law. Congress found that "without the continuation of the [Voting Rights Act's] protections, racial and language minority citizens will be deprived of their opportunity to exercise their right to vote, or will have their votes diluted, undermining the significant gains made by minority voters in the last 40 years."

In 2009, the Supreme Court expressed great doubts about the constitutionality of the extension of the Voting Rights Act. In Northwest Austin Municipal Utility District No. 1 v. Holder (2009), Chief Justice John Roberts Jr., writing for the court in an 8-1 decision, noted great progress with regard to race discrimination in voting. He also said that Section 5 "imposes substantial federalism costs" in its intrusion into state election systems in a covered state. Roberts objected that Section 5 applies only in some states and that its application is based on a coverage formula created in 1972.

The court, though, did not declare the extension of Section 5 to be unconstitutional. Instead, the court said that its duty was to interpret the statute to avoid constitutional doubts and it construed the law to allow jurisdictions, including political subdivisions of a state, without a recent history of race discrimination in voting to "bail out" and avoid its requirements.

Now, in Shelby County, Alabama v. Holder, the constitutionality of the extension of Section 5 is squarely before the court. Was Congress justified in concluding that the law remains necessary? Congress did not come to this conclusion lightly or quickly. In 2005-2006, the House and Senate Judiciary Committees held 21 hearings, listened to 90 witnesses and compiled a record of more than 15,000 pages. Representative Jim Sensenbrenner (R-Wis.), then chairman of the House Judiciary Committee, described this record as "one of the most extensive considerations of any piece of legislation that the United States Congress has dealt with in the 27 1/2 years that I have been honored to serve as a Member of this body."

Congress then voted overwhelmingly to extend Section 5 for 25 years. Congress expressly concluded that voting discrimination persists in the covered jurisdictions, and that without Section 5, "minority citizens will be deprived of the opportunity to exercise their right to vote, or will have their votes diluted, undermining the significant gains made by minorities in the last 40 years."

The record before Congress supported this conclusion. For example, between 1982 and 2006, the Section 5 preclearance requirement blocked 750 discriminatory changes in election systems in covered jurisdictions. Another 205 discriminatory changes were withdrawn. Countless changes were not adopted because of the recognition that preclearance was unlikely. The continued discrimination in covered jurisdictions is further evidenced by 650 successful court challenges under Section 2 of the Voting Rights Act in these places. University of Michigan Law School professor Ellen Katz has done extensive studies and found that covered jurisdictions have only 25 percent of the country’s population, but account for 56 percent of the successful suits under Section 2. Another study, by Peyton McCrary of George Washington University Law School, which included published and unpublished decisions, found that 81 percent of all successful Section 2 cases were in the covered jurisdictions even though they only hold 25 percent of the nation’s population.

Nor is this over. Before the 2012 elections, of the 12 states with the largest Hispanic populations, seven adopted restrictive voting laws. Of the 10 states with the largest African-American populations, five adopted restrictive voting laws.

Race discrimination in voting, as in so many areas of society, continues. No one can deny that Section 5 of the Voting Rights Act has been hugely successful and an essential tool in preventing discriminatory election practices. It is far too soon for the court to declare victory.

For a half-century, conservatives have been proclaiming the need for judicial restraint. The court should practice exactly that and defer to the considered judgment of Congress that Section 5 of the Voting Rights Act remains a crucial weapon to ensure racial equality in voting and to protect the fundamental right to vote for all Americans.

Erwin Chemerinsky is dean and distinguished professor of law at the University of California, Irvine School of Law.