A unanimous U.S. Supreme Court affirmed that states must draw district lines to equalize the population within the districts, rejecting the plaintiffs’ argument that redistricting should equalize actual voters. In making the Evenwel v. Abbott ruling, the Court refused to give Texas the ability to choose between the two standards, as the state had requested. Drawing districts based on the number of actual voters would almost certainly result in more Republican-friendly districts.

Some observers believed Texas already had this power under Burns v. Richardson, which allowed Hawai’i to use registered voters as their reapportionment basis. In Evenwel, the Court did not ultimately close the door to using total voters instead of total population, but the uncertainty over the issue may deter states such as Texas from attempting to use total voters in the next round of redistricting. “Whether a state is permitted to use some measure other than total population is an important and sensitive question that we can consider if and when we have before us a state redistricting plan that, unlike [today’s Texas districts], uses something other than total population as the basis for equalizing the size of districts,” wrote Justice Samuel Alito in a concurring opinion.

Nonetheless, Attorney General Ken Paxton said in a statement that he was pleased with the Court’s decision.

Justice Ruth Bader Ginsburg’s opinion held that using total population was consistent with the Constitution, which requires total population to be used to apportion U.S. representatives among the states. Further, ruling otherwise “would upset a well-functioning approach to districting that all 50 states and countless local jurisdictions have long followed.”

The Brennan Center for Justice estimated that every state legislative district map in the U.S. would be unconstitutional if the plaintiffs’ standards were required. In Texas, 63% of state House and 43% of state Senate seats would have been unconstitutional.