Philadelphia ? Among the most notorious on-screen gaffes ever, Janet Jackson’s breast-baring “wardrobe malfunction” on CBS during the 2004 Super Bowl halftime show drew a $550,000 indecency fine from the Federal Communications Commission. Now a federal appeals court has thrown it out.

A panel of the 3rd U.S. Circuit Court of Appeals ruled Monday that the FCC “acted arbitrarily and capriciously” in issuing the fine for the fleeting image of nudity, which it noted lasted just over half a second. An estimated 90 million people watching the Super Bowl heard Justin Timberlake sing, “Gonna have you naked by the end of this song,” as he reached for Jackson’s bustier.

The court said the FCC deviated from its nearly 30-year practice of fining indecent broadcast programming only when it was so “pervasive as to amount to ‘shock treatment’ for the audience.”

Duke University law professor Stuart M. Benjamin, a telecommunications law expert, called the decision “a slap in face for the FCC.” But the long-term significance of Monday’s ruling is uncertain, given the Supreme Court’s decision to take up a broadcast indecency case this year.

FCC Chairman Kevin J. Martin said he was surprised by the decision and disappointed for families.

“I continue to believe that this incident was inappropriate, and this only highlights the importance of the Supreme Court’s consideration of our indecency rules this fall,” Martin said.