The high desert city violates the California Voting Rights Act by using an election format that dilutes the influence of minority voters, Los Angeles County Superior Court Judge Mark V. Mooney wrote in his interim decision this week.
In the ruling, Mooney said he didn't consider voter turnout or the effectiveness of past campaigns, only voting patterns. He pointed out that intent to discriminate is not required to prove a violation.
"Plaintiffs' evidence established that racially polarized voting occurred in the city council elections for the City of Palmdale," he wrote.
The judge said if no appeals are filed he will set a hearing to discuss the implementation of remedies to the problem.
But City Attorney Matthew Ditzhazy said Thursday that Palmdale planned to appeal.
Ditzhazy objected to Mooney's definition of "racially polarized" and pointed out that a majority of California cities use an at-large method of electing councilmembers similar to Palmdale's.
"If the Legislature wanted to force every city into districts, it would have done so," Ditzhazy said. "This is one of the many issues we believe are ripe for appeal."
The Voting Rights Act has been used to sue several cities since it was adopted in 2002. One was Modesto, which switched to district voting as a result.
When Palmdale put the issue to a vote in 2001, Ditzhazy said, residents favored the at-large system.
The lawsuit was filed in April 2013 by Juan Jauregui, a resident of the city about 70 miles north of Los Angeles.
Earlier this year the mayor of neighboring Lancaster, R. Rex Parris, announced he had signed on as co-counsel for the suit against Palmdale, a city of about 150,000 where he grew up and has a high school named after him.
"Despite a Latino population of approximately 54.4 percent and an African-American population of 14.8 percent in the city of Palmdale, only one Latino and not a single African-American has ever been elected to Palmdale's City Council," Parris, a prominent litigation attorney, said in a January statement.
Ditzhazy accused Parris and his co-counsel, Malibu attorney Kevin Shenkman, of "using a poorly drafted statue as a pretext for a huge attorney's fee windfall."
"This lawsuit has never been about white, black or brown only green," he said.
Parris' city, with a population of about 159,000, is 38 percent Hispanic and 21 percent black. It also elects its City Council members at large and has one Hispanic council member and no black members.
The neighboring Antelope Valley cities, once small desert towns, grew rapidly during a suburban housing boom that began in the 1980s. The area has long been a hub for aviation, with the Air Force's Plant 42, where the B-2 bomber and other planes have been assembled, located in Palmdale.
Associated Press writer John Rogers contributed to this report.