On Monday, the U.S. Supreme Court chose not to weigh-in on the six-year-old copyright battle alleging that Led Zeppelin's 1971 hit "Stairway to Heaven" plagiarized the opening riff from Spirit's "Taurus," with "Taurus" being a song that had come out three years earlier. As a result, a ruling was left in place that rejected the copyright allegations that claimed violations on the part of Zeppelin's Jimmy Page and Robert Plant, both of whom are credited as the songwriters for "Stairway to Heaven."
The steps that brought us to Monday's conclusion began more than half-a-decade ago with the filing of the initial suit, which was put together by journalist Michael Skidmore on behalf of the estate of Spirit's frontman (Randy Wolfe). Lawyers working on behalf of Wolfe's estate claimed that Led Zeppelin became aware of Spirit's song when, in 1970 (see: a year before "Stairway to Heaven" came out) the two bands were on the same bill. In 2016 that suit lost at trial, with a jury reaching a conclusion that the two songs weren't "intrinsically similar." But two years later it was given another go after it was taken up by the 9th Circuit Court of Appeals.
That court ended up issuing an en banc ruling that was seen as a win for the music industry, which had felt like it was under attack by spurious copyright claims following the 2015 trial over whether "Blurred Lines" stole from Marvin Gaye or not (note that it was ruled that it did).
After the 9th Circuit ruled against him, Skidmore took his appeal to the Supreme Court.
“The ‘Court of Appeals for the Hollywood Circuit’ has finally given Hollywood exactly what it has always wanted: a copyright test which it cannot lose,” Skidmore’s attorneys reasoned, according to Variety. “The effect of this ruling is a gift to the industry, a disaster for independent artists, and spells the end of any real copyright protection for musical works.”
On top of that, Skidmore's lawyers said that the 2016 verdict against them was flawed because jurors in the case weren't able to hear "Taurus" via an album recording, and instead had to rely upon sheet music given to the U.S. Copyright Office. That was one of the "errors" that allowed for a retrial. However, the 9th Circuit reasoned that the 1909 Copyright Act, which doesn't protect music recordings, had been correctly interpreted by the judge.
Far more recently (again, today) the Supreme Court opted not to comment on its decision, with BBC adding that millions of dollars could've been at stake if the court had actually chosen to hear it.