WASHINGTON - A special federal court ruled yesterday that a key component of the Voting Rights Act was constitutional, rejecting a challenge from a city utility board in Texas.

Under the landmark law, which Congress extended in 2006 for an additional 25 years, states and towns with histories of racial discrimination must get Justice Department or court approval before making any changes to the way elections are conducted.

The law was intended to keep state and local governments from passing laws that made it harder for minorities to vote.

Shortly after Congress extended the law, Northwest Austin Municipal Utility District Number One, a government board formed to provide local services to about 3,500 people, sued.

The board asked the panel to exempt it from the law and said Congress had no constitutional right to pass a bill that tried to remedy past discrimination.

Under the law, voting-rights challenges go before a court made up of district and appellate judges in Washington.

The court ruled that the utility board did not qualify as a "political subdivision" and could not be exempted from the law. It also ruled that racial discrimination in voting persisted and that Congress acted appropriately when it extended the law.

Any appeal of yesterday's decision would go directly to the Supreme Court.