Judge George H. King ruled that Warner/Chappell never had the right to charge for the use of the "Happy Birthday To You" song. Warner had been enforcing a copyright since 1988, when it bought Birch Tree Group, the successor to Clayton F. Summy Co., which claimed the original disputed copyright.
The judge ruled that a copyright filed by the Summy Co. in 1935 granted only the rights to specific piano arrangements of the music, not the actual tune.
A spokesman for Warner/Chappell, the publishing arm of Warner Music, said, "We are looking at the court's lengthy opinion and considering our options."
The plaintiffs' attorneys had characterized the years-long legal fight as a David vs. Goliath battle that pitted independent filmmakers against a large corporation collecting profits on a song whose authors had long since died.
Tuesday's ruling means that the song is now considered a public work and is free for everyone to use without fear of having to pay for it, according to a statement from the plaintiffs' attorneys.
Jennifer Nelson, one of the filmmaker plaintiffs and owner of Good Morning to You productions, called the decision a "great victory for musicians, artists and people around the world who have waited decades for this."