The Supreme Court ruled Monday to tear down part of the Voting Rights Act, exempting a Texas district from the rules aimed to protect minorities prevented from going to the polls.

"The historic accomplishments of the Voting Rights Act are undeniable, but the act now raises serious constitutional concerns," wrote Chief Justice John Roberts.

The court avoided the major constitutional questions raised in the case over the federal government's most powerful tool to prevent discriminatory voting changes since the mid-1960s.

The law requires all or parts of 16 states, mainly in the South, with a history of discrimination in voting to get approval in advance of making changes in the way elections are conducted.

The opinion is significant and narrow at the same time. The court has only ruled that all electoral entities have the right to challenge the "pre-clearance" provision of the VRA. The ruling does not overturn the provision (or any other part of the VRA) but does lay down a legal marker to challenge the constitutionality of the act itself.

"Whether conditions continue to justify such legislation is a difficult constitutional question we do not answer today. We conclude instead that the Voting Rights Act permits all political subdivisions, including the district in this case, to seek relief from its pre-clearance requirements."

The court said Monday that the Northwest Austin Municipal Utility District No. 1 in Austin, Texas, can opt out of the advance approval requirement, reversing a lower federal court that found it could not.

The nearly unanimous opinion of the court featured a partial dissent from the court's lone African American Justice, Clarence Thomas, who said he would have ruled the VRA unconstitutional. Thomas wrote that while he agrees with the court's judgment, it is too narrow. He would have gone a step further and held that the pre-clearance provision is unconstitutional.

The Associated Press contributed to this report.