(Reuters) - Led Zeppelin on Monday persuaded a U.S. appeals court to reinstate a jury verdict that it did not steal the opening guitar riff for "Stairway to Heaven" from an obscure song written four years earlier.

In a 9-2 decision, the 9th U.S. Circuit Court of Appeals in San Francisco said lead singer Robert Plant's and guitarist Jimmy Page's 1971 rock anthem did not infringe "Taurus," written by guitarist Randy Wolfe of the band Spirit.

"The trial and appeal process has been a long climb up the 'Stairway to Heaven,'" Circuit Judge Margaret McKeown wrote for the majority.

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Wolfe, who performed as Randy California, drowned in 1997, but a trustee for his estate sought damages potentially reaching millions of dollars.

"Obviously, the court got it wrong," the trustee's lawyer, Francis Malofiy, said in an interview. "This is a big loss for creators, those who copyright laws are meant to protect." Malofiy said he may appeal to the U.S. Supreme Court.

Lawyers for Led Zeppelin did not immediately respond to requests for comment.

The decision in the five-year-old case was a victory for a music industry still combating fallout from a 2015 verdict that Robin Thicke's and Pharrell Williams' 2013 smash "Blurred Lines" copied Marvin Gaye's 1977 hit "Got to Give It Up."

Jurors awarded Gaye's children $7.4 million, which was later reduced to $5.3 million. The singer Katy Perry is appealing a $2.8 million verdict reached last August in a separate copyright case over her song "Dark Horse."

Wolfe's trustee, Michael Skidmore, said "Stairway" and "Taurus" had similar chord progressions, and that Page may have written "Stairway" after hearing "Taurus" while Led Zeppelin and Spirit toured together.

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In a June 2016 verdict, jurors found that while Plant and Page had access to "Taurus," its riff was not intrinsically similar to "Stairway."

Jurors were not allowed to listen to "Taurus," and Monday's decision found this and other alleged errors did not require a new trial.

More importantly, the appeals court ditched its "inverse ratio" rule, which says the more access songwriters have to earlier works, the lower the bar for proving substantial similarity.

McKeown said the rule "defies logic," given how the concept of access has become "increasingly diluted" as more songs become available on Netflix, Spotify, YouTube and other platforms.

She also said minor song similarities might not support infringement claims. "We have never extended copyright protection to just a few notes," she wrote.

Five of the six federal appeals courts to consider the inverse ratio rule now reject it. The 9th Circuit covers California and eight other Western states.

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The case is Skidmore v Led Zeppelin et al, 9th U.S. Circuit Court of Appeals, No. 16-56057.

(Reporting by Jonathan Stempel in New York, Editing by Rosalba O'Brien and Jonathan Oatis)