The United States Supreme Court on Wednesday left open the possibility of further limiting the use of racial criteria in drawing electoral districts, a move that could undermine the last major pillar of the historic Voting Rights Act, which for more than half a century has empowered minority voters and candidates.

The Court’s conservative majority appeared to agree with the arguments of lawyers for Louisiana and the Trump administration, who argued that race played too large a role in the decision to create a majority African-American second district in the state, in violation of the constitutional principle of equal treatment of all citizens.

Several of the conservative justices have been looking for ways to set limits on how and when states can consider race in the redistricting process, a change that could have a big impact on elections.

A decision that would repeal or limit Section 2 of the Voting Rights Act would likely reduce the number of minority voters and upset electoral maps across the country.

Judge Brett Kavanaugh noted that recent court decisions recognize that “race-based measures are permissible, but should not be in place indefinitely,” while the two-hour-plus hearing appeared to focus on what that time limit might be.

Chief Justice John Roberts chimed in at another point in the debate asking, “What’s the right measure?”, referring to how big a role race should play in drawing electoral districts.

Those two justices (Roberts and Cavanaugh) had cast the deciding votes to uphold an important part of the Voting Rights Act in a decision two years ago. However, this time, their comments indicated a willingness to review how that law is applied to redistricting decisions.

Wednesday’s hearing was an unusual reexamination of the case, which the Supreme Court had already discussed during the previous court session.

In August, the court had asked the parties involved to consider whether Section 2 of the Voting Rights Act violated the 14th and 15th Amendments to the Constitution, which were passed after the American Civil War to guarantee black citizens citizenship, equal treatment and the right to vote.

Article 2 requires states, under certain circumstances, to draw electoral districts so that African-American and other minority voters have an effective opportunity to elect candidates of their choice.