In a hearing before the 2014 elections, Judge Schroeder, an appointee of George W. Bush, declined to impose a preliminary injunction of the election law. He was overruled by the United States Court of Appeals for the Fourth Circuit, which found evidence of an unconstitutional impact and laid out new principles for evaluating changes in election law. But the Supreme Court lifted the injunction, without comment, perhaps because it did not want to alter the rules too close to the fall elections.

Image Protesters at the N.A.A.C.P. rally. Credit... Travis Dove for The New York Times

Once federal oversight was ended by the Supreme Court decision in 2013, legislators rushed through a battery of changes without offering any convincing reasons, said Penda D. Hair, a lawyer representing the North Carolina N.A.A.C.P., in an opening statement.

“They were voter suppressors in search of a pretext,” said Ms. Hair, who is co-director of the Advancement Project, a civil rights legal group in Washington.

The state, in its opening comments, said that the measures were adopted to enhance voter confidence and achieve administrative savings, and that they were not discriminatory because they affected all races equally.

The state’s lawyers also accused the plaintiffs of making emotional appeals to past racial conflicts, like the refrain of the state branch of the N.A.A.C.P. in the weeks leading up to the trial that “This is our Selma.”

“What is the dastardly thing North Carolina has done?” asked Thomas A. Farr, a private lawyer who is defending the state. The state, he said, has created election conditions that are common across the country. Some other states, like New York, do not have early voting, same-day voting or out-of-precinct voting, he noted.

But it is the particular conditions and their context in North Carolina that are at issue, say many legal experts.