Singers Justin Timberlake and Janet Jackson are seen during their performance prior to a wardrobe malfunction during half time at Super Bowl XXXVIII in Houston. (DAVID PHILLIP/AP)

A federal appeals court Wednesday tossed out — again — the $550,000 fine that the Federal Communications Commission slapped on CBS stations in 2004, after the network aired a half-second of Janet Jackson’s right nipple during the that year’s Super Bowl halftime show.

The U.S. Court of Appeals for the Third Circuit (in Philly) stuck by its guns, having already spit out a similar ruling against the FCC fine in July of ’08.

But the U.S. Supreme Court suggested that the three-judge panel to think again in light of the high court’s decision in a separate ruling that had to do with the FCC, Fox stations, Nicole Richie and Cher (the two women had used some pretty colorful language during music trophy show broadcasts on Fox). The Supreme Court ruled that the FCC could fine broadcast TV stations for unscripted or fleeting instances of naughty stuff.

So in February of 2010, the appeals court in Philly heard another round of discussion about the half-second broadcast-TV debut (actually nine sixteenths of a second, according to somebody who actually clocked it) Janet Jackson’s right breast.

And, on Wednesday, the court, 2-to-1, ruled that the FCC had, after three decades of giving a pass to the “fleeting” stuff, acted arbitrarily when it fined CBS over Jackson’s mammary without having first sent out a memo letting networks know about any changes to the fleeting-naughty-bits policy.

In round numbers: the court said that fleeting expletives and fleeting nudity have much in common, but that if the FCC is going to change its policy, it can’t do it retroactively — particularly when handing out fines. The FCC needs to tell networks in advance, not after the fact, the court said.

Here’s how the court put it: “The FCC failed to acknowledge that its order in this case reflected a policy change and improperly imposed a penalty on CBS for violating a previously unannounced policy.”

And here’s how watchdog group Parents TV Council interpreted that:

“Parents and Families Outraged: Janet Jackson Super Bowl Striptease Not Indecent.”

“Today’s ruling reaches the level of judicial stupidity and is a sucker-punch to families everywhere,” PTC president Tim Winter said Wednesday.

“When CBS aired the now-infamous Janet Jackson striptease, the response was an unprecedented national uproar,” Winter remembered fondly.

“How can nudity and a striptease in front of 90 million unsuspecting TV viewers not qualify as indecency?” he continued, warming to his theme.

“We urge the FCC and our nation’s High Court to include this outrageous Circuit Court opinion in its judicial review of the broadcast decency law, which is currently before the Court,” Winters concluded.

CBS has steadfastly insisted it too was sucker-punched by Jackson and Justin Timberlake’s stunt — he’s the one who did the bodice ripping that introduced Jackson’s right breast to those 90 million football fans. And CBS, and other broadcasters, have instituted several-second delays to most live television events — except, of course, live news programming — and sports.

“We are gratified that, once again, the court has ruled in our favor,” CBS said in a statement issued Wednesday. “We are hopeful that this will help lead the FCC to return to the policy of restrained indecency enforcement it followed for decades.”