“The court today does great damage to that right of equal opportunity,” she wrote. “Not because it denies the existence of that right, but because it refuses its enforcement.”

A three-judge panel of the Federal District Court in San Antonio had ruled that a congressional district including Corpus Christi denied Hispanic voters “their opportunity to elect a candidate of their choice.” The court rejected a second congressional district stretching from San Antonio to Austin, saying that race had been the primary factor in drawing it. In a separate decision, the court found similar flaws in several state legislative districts.

The Supreme Court reversed almost every part of those rulings, though it did hold that a state House district in Tarrant County was an impermissible racial gerrymander.

There was an odd wrinkle in the case: The San Antonio court itself had for the most part endorsed the contested maps in 2012, after the Supreme Court rejected earlier ones and told the court to try again. The 2012 maps, the panel later said, had been considered in haste in advance of pending elections. In 2013, the Texas Legislature decided not to draw new maps and instead mostly adopted the one drawn by the San Antonio court.

After three election cycles using the interim maps, the court ruled that they were flawed. “Although this court had ‘approved’ the maps for use as interim maps, given the severe time constraints it was operating under at the time of their adoption,” the court said, that approval was “not based on a full examination of the record or the governing law” and was “subject to revision.”