The Supreme Court heard arguments last week on a key part of the Voting Rights Act designed to protect against racial discrimination at the polls. The case could upend the way certain parts of the country make changes to voting laws. Some questions you may have about the law:

Q: What is the Voting Rights Act, and how long has it been in force?

A: Signed into law by President Lyndon Johnson in 1965, the sweeping legislation was designed to prevent racially discriminatory voting practices.

Q: What is this “Section 5” we keep hearing about?

A: This is the part of the Voting Rights Act under review by the high court. The act stipulates that areas of the country with a history of racial discrimination must receive preclearance from the Justice Department or a federal court before making any election law changes.

Q: How many states are subject to the restrictions in Section 5?

A: Alabama, which is the subject of the Supreme Court case, and eight other states, as well as some other jurisdictions elsewhere are subject to Section 5. Most of the states are in the South.

Q: After all these years, what’s the issue now?

A: Over the years, Congress has reauthorized Section 5 several times, most recently in 2006. That decision is at the heart of the current case involving Shelby County, Ala. The question before the court is whether Congress’ 2006 reauthorization — which extended the provision for another 25 years — exceeded its constitutional authority.

Q: Why do opponents want to do away with Section 5?

A: They say it is outdated. “The violence, intimidation and subterfuge that led Congress to pass Section 5 and this court to uphold it no longer remains,” says the Shelby County challenge. And the formula still relies on election data from 1972.

Q: And why do supporters want to keep Section 5?

A: They believe it’s still a necessary preventive measure against changes to voter ID laws, district lines and other adjustments that could impede the rights of minority voters.

Q: What might the Supreme Court do next about the Voting Rights Act?

A: That’s not clear. But it’s worth bearing in mind that in 2009, Chief Justice John Roberts signaled receptivity to the argument that the provision is outdated.

“Things have changed in the South,” he wrote, adding: “The evil that Section 5 is meant to address may no longer be concentrated in the jurisdictions singled out for preclearance. The statute’s coverage formula is based on data that is now more than 35 years old, and there is considerable evidence that it fails to account for current political conditions.”