SANTA ANA, Calif. — Nearly two months after a federal jury decided that a notorious motorcycle club must forfeit the rights to its trademarked emblem, a judge on Thursday nullified the verdict, finding that seizure of the intellectual property was unconstitutional.

In a 51-page ruling, U.S. District Judge David O. Carter said the government’s strategy of trying to devastate the Mongols motorcycle club by confiscating its treasured Genghis Khan-style logo would violate the group’s First Amendment right to free speech and the excessive fines clause of the Eighth Amendment.

The decision upended years of efforts by prosecutors to weaken the Mongols, which a federal jury in January deemed a criminal enterprise after finding the group guilty of racketeering and racketeering conspiracy for the crimes of murder, attempted murder and drug dealing. In the second phase of that wide-ranging, eight-week trial, the jury found that the Mongols must give up their rights to the emblem, which is emblazoned on the vests, T-shirts and motorcycles of hundreds of members.

But Carter declined to order the Mongols to forfeit the logo until he had a chance to review their arguments and consider their free speech rights.

“The Mongol Nation’s and its members’ right to express their identity through the noncommercial display of symbols constitutes speech subject to First Amendment protections,” Carter wrote in the ruling released Thursday. He added that the First Amendment bars the government from using forfeiture laws in racketeering cases “to chill this expression.”

Carter further wrote that since the jury determined that the Mongols logo was forfeitable only on the racketeering conspiracy count, but not racketeering itself, taking away the insignia was an inordinate punishment.

What’s more, Carter wrote, “There is no evidence that forfeiture of collective membership marks will lead to a less violent or capable organization.”

The Mongols, who feared that losing the rights to their logo — a brawny Genghis Khan-like man sporting a queue and sunglasses and riding a chopper while brandishing a sword — would have severe consequences, hailed the ruling as not just a victory for the group, but for other biker clubs that law enforcement authorities have tried to take down.

“The Mongols MC is ecstatic that they could successfully defend the First Amendment for themselves and all motorcycle clubs,” the club’s general counsel, Stephen Stubbs, said. “Today, Judge Carter stood strong against the United States government’s attempt to ban symbolic speech in an epic win for all Americans.”

Carter’s ruling was a severe setback for California prosecutors who spent more than a decade going after the Mongols patch.

A spokesman for the U.S. attorney’s office for the Central District of California, Thom Mrozek, said in a statement that prosecutors were disappointed by the decision and that they believed Carter was required by law to issue the forfeiture order that the government had requested. He said the office was considering an appeal.

“While affirming the jury’s guilty verdicts on racketeering charges, the court’s ruling nullifies the jury’s finding that these marks are a core component of the Mongols’ decadeslong pattern of murder, assault and drug trafficking,” Mrozek said.

The roots of the government’s case date to 2005 when four undercover agents for the Bureau of Alcohol, Tobacco, Firearms and Explosives managed to become full members of the Mongols.

The result was a jarring blow to the club. In October 2008, a grand jury returned an 86-count federal racketeering indictment against 79 Mongols, accused of crimes ranging from murder to drug trafficking to money laundering. Except for one defendant who died in custody and another who was deemed incompetent, all others eventually pleaded guilty.

Donald Charles Davis, who writes the biker blog “The Aging Rebel,” said he felt Carter’s ruling was “inevitable.”

“The government’s ambition was blatantly unconstitutional,” Davis said. “The government sought to turn symbols like the Mongols insignia, the club’s name and sentiments associated with the club like ‘Support The Mongols,’ into contraband.”

Carter’s ruling was drawn from a flood of legal opinions that were submitted by academics, law firms and think tanks. He upheld the Mongols’ convictions on racketeering and racketeering conspiracy, and tentatively granted the forfeiture of the various weapons and property that had been seized.

Despite certain members of the club wearing the symbols “while committing violent crimes” or being “rewarded with other patches for the commission of crimes” that did not justify the forfeiture of the logo, Carter wrote.

David Santillan, national president of the Mongols, pumped his fist into the air as the decision was read before a courtroom audience that included several Mongols members.

“He upheld our constitutional rights, not only as the Mongols motorcycle club, but as citizens,” Santillan said. “A big weight has been lifted off the club’s shoulders.”

This article originally appeared in The New York Times.