The community of Canyon Creek was ranchland rich with limestone and cedar trees when Jim Crow held sway in the South. The first house wasn't built until the late 1980s and not even a hint of discrimination attaches to this little slice in suburbia.

President Barack Obama won more than 48 percent of the vote in November in this overwhelmingly white community northwest of the state capital.

Yet Canyon Creek, the heart of Northwest Austin Municipal Utility District Number One, is the site of a major Supreme Court battle over the federal government's often used and most effective tool in preventing voting discrimination against minorities.

The utility district's elected five-person board manages a local park and pays down bond debt. Because it is in Texas, the board is covered by a section of the Voting Rights Act that requires approval from the Justice Department before any changes can be made in how elections are conducted.

That requirement applies to all or parts of 16 states, mostly in the South, with a history of preventing blacks, Hispanics and other minorities from voting.

The utility district is challenging that section of the law, which Congress extended in 2006 for 25 years. The Obama administration is defending it.

The Voting Rights Act, enacted in 1965, opened the polls to millions of black Americans. The law "has been the most important and transformative civil rights act in our country's history," said John Payton, director of the NAACP Legal Defense and Educational Fund.

The federal government has used the provision, known as Section 5, to "stop things that would have perverted our democracy," Payton said. His group represents Texans and organizations seeking to preserve the section.

On the other side are the utility district, an array of conservative legal groups and some Southern Republicans.