Not only should Nike appeal this decision to the U.S. Supreme Court, the advertising industry's organizations should encourage it to do so and provide whatever support Nike may request.
Under attack by critics, Nike has not been shy about defending itself from charges that its products are manufactured in Asian "sweatshops." It's mounted that defense using the advertising and public relations tools at the disposal of a company of its size. But that doesn't turn its defense into "advertising." Nike's policies regarding overseas labor standards may be relevant to some consumers, those who want to make a "socially responsible" product choice. But Nike has not built its "reason to buy" around its overseas labor policies.
What Nike does, or does not do, is fair game for open and robust public debate. But neither its critics nor Nike should face burdens that hamper their ability to debate those issues if the burdens are not necessary and equally shared. The California Supreme Court majority does not suggest that Nike's critics must have their claims scrutinized in court for their veracity, but it demands that Nike run that gamut. That means Nike, or any other business, runs a risk if it speaks out publicly when its practices are attacked. And that seriously compromises what "free speech" should be about.