A federal court on Friday found that Maricopa County Sheriff Joe Arpaio systematically violated the constitutional rights of immigrants through "saturation" sweeps that ended up targeting people based on their appearance or perceived ancestry.

The combative, colorful and controversial Mr. Arpaio has over the past decade come to define American anger over illegal immigration as he's aggressively pursued immigration lawbreakers in Arizona's most populous county, corralling a staggering 25 percent of all US immigration arrests per year.

But while Arpaio remains popular among many conservatives for stunts like investigating President Obama's birth certificate and issuing pink underwear to inmates, the court ruling can be seen as part of a broader pushback against aggressive immigration enforcement and growing momentum for a bipartisan solution to America's undocumented immigrant problem with implications both for illegal immigrants as well as Arpaio's own legacy.

The decision, which in essence agreed with an earlier lower court ruling, should be seen as "a warning to any agency trying to enforce 'show me your papers' [state laws] – there is no exception in the Constitution for immigration enforcement," said Cecilia Wang, director of the ACLU's Immigrants' Rights Project, in a statement.

In the ruling, US District Court Judge Murray Snow told Arpaio and his deputies to stop using race and ancestry as reasons to stop or detain drivers in a tactic widely known as "saturation patrols."

"The great weight of the evidence is that all types of saturation patrols at issue in this case incorporated race as a consideration into their operations," Judge Snow said in a written ruling.

Tim Casey, the county's lawyer, maintained that race has never been the prevailing factor in making decisions about whom to stop.

"The Maricopa County Sheriff's Office has always held the position that they never have used race and never will use race in making a law enforcement decision," Mr. Casey told Reuters, adding that Arpaio's office will "fully comply with the letter and spirit of this order."

But if the court ruling represents a victory for immigration advocates and a legal reversal for Arpaio, it's also clear that, even before the ruling, Arpaio had been losing support among more educated white voters even as opposition against him had galvanized among ascendant Hispanic voters, the Arizona Capital Times newspaper reported recently. Arpaio won reelection with only 50.7 percent of the vote last November, his lowest total.

“He was the most popular guy in the state, but he’s been on a long slow ride down,” Arizona political analyst Michael O’Neil told the newspaper.

Citing the bipartisan push for a federal solution to the undocumented immigrant problem as well as some states now moving toward allowing driver licenses for illegal immigrants, New York Times columnist Linda Greenhouse suggests that Arpaio, "representing for so long the leading edge of anti-immigration political activism, may by now have become the trailing edge."

But if Arpaio's law and order philosophy finds ultimate disfavor in the courts and society more broadly, he is also given wide credit for stepping up to push the porous border issue and in turn bolstering what has become a robust debate about one of the country's greatest conundrums.

In a 2011 debate with an immigration activist, Arpaio defended his enforcement of current immigration law, but also suggested that Washington get busy addressing reforms.

"If you don’t like the law, change the law,” Arpaio said at the time. “Maybe more visas. Listen, my mother and father came here from Italy. People here from Mexico, South America and all over the world made this country great.”

Arpaio's embodiment of public anger about porous borders, notes Ms. Greenhouse, "has given way to "the (mostly) serious conversation going on now in Washington."