The US Court of Appeals for the Federal Circuit wiped out (PDF) a sizable chunk of Apple's biggest legal win today, overturning parts of a 2012 jury verdict against Samsung that entitled the iPhone maker to $930 million in damages.

Apple won that trial on both patent claims and claims related to "trade dress," an amorphous part of trademark law. The Federal Circuit, which considers all patent appeals, said the trade dress claims weren't legally justified and threw them out. The Federal Circuit is leaving it to the lower court to issue a final judgment, but since those claims accounted for $382 million of Apple's big win, that's how much Apple is expected to lose. It's more than 40 percent of the verdict winnings, leaving $548 million on the table for Apple to collect.

In the view of the appeals judges, the iPhone's trade dress isn't protectable at all, because it's more functional than decorative. While Apple witnesses focused on the phone's "beauty," Samsung cited "extensive evidence in the record that showed the usability function of every single element in the unregistered trade dress." Things like rounded corners improve "pocketability" and "durability." The court also considered Apple's icons, packed 16 to a screen on iPhone 3 and iPhone 4, and found them not protectable as trade dress.

The Apple v. Samsung jury found that both Apple's unregistered and registered trade dress were infringed by various Samsung phones; the appeals court found both unprotectable.

Samsung lawyers also appealed their loss on design and utility patents but weren't able to make any headway, and those wins will stand. In particular, Samsung challenged the jury's award of "lost profits," saying it was unfair to take away the profits from an entire phone because of particular infringing features. But the appeals court the law clearly allows for liability to the extent of a patent infringer's "total profit."

In a footnote addressed to law professors who filed an amicus brief saying the damages rule "makes no sense in the modern world," the judges write that those are "policy arguments that should be addressed to Congress."

Neither Apple nor Samsung have yet publicly responded to the appeals decision.

Today's ruling applies to the 2012 verdict only. It doesn't address a second Apple v. Samsung lawsuit, which resolved in 2014 with a smaller jury verdict of $120 million.