The US Supreme Court voted unanimously Monday to uphold the "one person, one vote" legal principle, blocking a conservative legal challenge in Texas that would have redrawn voting districts based on eligible voters rather than total population.

The eight justices, minus Antonin Scalia, who died on February 13, ruled against two rural Texas voters who argued that districts should only count eligible voters, excluding people who cannot vote, such as non-citizens and children. The petitioners claimed that the way districts in the state are drawn dilutes the power of their vote in favor of people living in cities, which have larger minority and non-voting populations.

A ruling for the challengers could have potentially upset the political balance in a number of states by shifting voting clout away from urban areas that are more racially diverse and where Democrats hold sway, and redirecting it to Republican-ruled rural areas that are largely white. The states most affected would have been those with large numbers of non-citizen residents like Texas, California, New York, Nevada, and Arizona.

The decision, penned by liberal Justice Ruth Bader Ginsburg, said Texas's method of drawing districts does not violate the long-established legal principle of "one person, one vote" endorsed by the Supreme Court in the 1960s during the American civil rights era. All 50 states currently draw their legislative districts according to this principle.

Ginsburg wrote that "total-population apportionment meets the equal protection demand, by rendering each representative alert to the interests and constituent-service requests of all who dwell in the representative's district."

She said the ruling was based on "constitutional history, the court's decisions and longstanding practice" that says states may draw legislative districts based on total population. Adopting a new approach "would upset a well-functioning approach to districting that all 50 states and countless local jurisdictions have followed for decades, even centuries," she added.

The decision does not force all states to use total population to draw boundaries, and does not rule out on the possibility that states could switch to a different method of redistricting. It only denied the petitioner's challenge, which specifically tried to force the state to change to counting only eligible voters.

Two of the court's most conservative justices, Clarence Thomas and Samuel Alito, concurred with the judgment, but did not sign on to Ginsburg's opinion.

Thomas wrote separately that the Supreme Court "has never provided a sound basis for the one-person, one-vote principle" and the Constitution still allows states the freedom to draw districts based on various methods and population counts.