Yes. California's Uniform Trade Secrets Act prohibits the theft or disclosure of legitimate commercial secrets. The state law does not distinguish between rogue employees, corporate spies, and the media, all of whom can be liable under the act. Nor does it matter that Gizmodo obtained the information secondhand--what's important is the fact that the prototype was a secret and the tech blog either knew or should have known that it was acquired improperly. Both of these conditions seem to be satisfied, according to Gizmodo's own account of what happened.
Here's the story: Gizmodo's source allegedly found the iPhone prototype at a bar, asked around to see if it belonged to somebody, called Apple HQ to leave a message, and then sold the device to Gizmodo for $5,000. He didn't hand it to the bar tend. He didn't tell the police. Gawker Media had a legal responsibility to ensure that the seller rightfully possessed the property. They did not. And if sued, they might have to pay, which would make this purloined iPhone the most expensive Apple product in history.
Daily Finance's Jeff Bercovici concludes: "What Gawker Media did here was egregious. I doubt Steve Jobs will sue, but if he does, he will have justice on his side."