The Supreme Court will hear argument later this month in Shelby County v. Holder, which challenges a key provision of the landmark Voting Rights Act. Congress voted in 2006 to reauthorize and extend Section 5, the cornerstone of the legislation, for an additional 25 years.

Why is Section 5 so important? Because it protects voters in jurisdictions with a history of severe racial discrimination at the polls. Before any of those “covered jurisdictions” change their practices or procedures affecting voting, they must seek approval from the federal government. The law continues to protect American voters from unjust efforts to make it harder for them to vote.

Look no further than the rash of efforts in states like Florida, Texas and South Carolina to cut-back early voting, curtail voter registration drives, and mandate forms of identification that millions of law-abiding Americans lack. As Lyle Denniston writes for SCOTUS Blog, “the Voting Rights Act [] is now widely credited as the most effective civil rights law in American history.”

Now a county in Alabama is suing to strike down Section 5 as unconstitutional. We disagree.

And last week, Common Cause joined an amici brief to the Supreme Court explaining our reasons. Spearheaded by the Leadership Conference on Civil and Human Rights, we were privileged to join with 28 other organizations in one voice, including the Anti-Defamation League, AARP, the Center for American Progress, the League of Women Voters, National Urban League, Demos, the National Education Association, and the Southern Poverty Law Center.

You can read the brief here.

In it, we argue that “[w]hile many [covered] jurisdictions have made substantial progress toward eliminating discriminatory voting practices, the legislative record amassed by Congress — as well as more recent history — shows that these gains are fragile and that discriminatory practices still persist.”

Should the Supreme Court strike down Section 5, “there is a real and substantial risk that the progress made in the covered jurisdictions since 1965 would be rolled back.” Most starkly, it means a high likelihood “that millions of minority voters will face new barriers to the exercise of their most fundamental political right.”

Common Cause has a long history of supporting the Voting Rights Act, including its renewal in 2006 and 1982. Common Cause’s former chairman emeritus, the late Archibald Cox, defended the constitutionality of the Voting Rights Act before the Supreme Court in 1966.