The Supreme Court is hearing arguments on Wednesday in a major voting rights case. Here is some of the history of the law and the issues that are likely to be raised before the court.

Q. What did the Voting Rights Act do?

A. The Voting Rights of Act of 1965 addressed pervasive lawless conduct by Southern officials bent on denying blacks the right to vote. The act’s central innovation was its requirement that jurisdictions with a history of discrimination get permission from the federal government — the Justice Department or a federal court in Washington — before making changes to voting procedures. The requirement, in Section 5 of the law, applied to changes large and small, from moving a polling place to redistricting an entire state. It was a significant intrusion on state sovereignty and was initially meant to last for just five years.

Q. Which states does it apply to, and how was that list determined?

A. Section 5 at first applied to states and localities that met two criteria. The first was using a device like a literacy test to restrict the opportunity to register and vote. The second applied if fewer than 50 percent of people old enough to vote were registered in November 1964, or if fewer than 50 percent of them voted in the presidential election that year. Using that formula, all of Alabama, Alaska, Georgia, Louisiana, Mississippi, South Carolina and Virginia were covered, along with parts of Arizona, Hawaii and Idaho.

The law was extended for five years in 1970, using data from 1968.

In 1975, Congress extended the law for seven years. It also expanded it to cover discrimination against members of “language minority groups” in places that used only English-language ballots even though substantial numbers of people spoke another language. The extension relied on data from 1972. The new formula meant that all of Alaska, Arizona and Texas were covered, along with parts of California, Florida, Michigan, New York, North Carolina and South Dakota.