This week, in one of the most important voting rights cases in decades, the Supreme Court will hear oral argument in Shelby County v. Holder, a constitutional challenge to a core provision of the Voting Rights Act. The Voting Rights Act is perhaps the most successful civil rights law in our nation’s history, which has protected the right to vote for millions of Americans. Shelby County argues that this iconic statute is now outdated, and that bipartisan majorities of Congress violated the Constitution when they voted by huge margins to renew this celebrated law in 2006.

The biggest problem with Shelby County’s argument is the Constitution itself, which explicitly gives to Congress broad power to “enforce” by “appropriate legislation” the Constitution’s prohibition on racial discrimination in voting. In the Voting Rights Act, Congress used this express power to ensure that the right to vote would be a reality for all persons regardless of race.

Shelby County argues that the South has changed, but Congress—the body specifically charged in the text with enforcing the Constitution’s command of equality in the voting booth—disagreed. In 2006, amidst progress, Congress found continuing racial discrimination in voting, concentrated in many of the same states that resisted the 15th Amendment and made the Voting Rights Act a necessity. In places like Selma, Ala.— which played a historic role in the law’s enactment in 1965—governments sought to strip minorities of hard-won gains at the very moment racial minorities were about to succeed at the polls. Elsewhere, white elected officials even went to the extreme of cancelling an election to prevent African-Americans from electing their candidate of choice. The Voting Rights Act continues to play an essential role in preventing discriminatory voting changes such as these.

Shelby County should be an easy case. The Constitution’s text expressly gives to Congress the power to enforce the Constitution’s prohibition against racial discrimination in voting, arming Congress with substantial power to ensure that our most precious fundamental right is enjoyed by all Americans regardless of race. The Supreme Court has repeatedly upheld this very act, and the record developed by Congress shows that racial discrimination in voting is still a blot on our Constitution’s promise of voting equality. The question now, as the justices hear oral argument, is whether the Roberts Court will follow the Constitution or subvert it.