The holding of today's opinion both is important and can be concisely summarized. Whether a party who didn't sign an arbitration agreement can nonetheless be compelled to arbitrate (e.g., as an alter ego, as estoppel, etc.) is an issue for the court, not the arbitrator. And it doesn't matter that JAMS rules say the contrary. The court decides.
Plus, it's a California case, which means there's always the possibility of celebrity involvement. As the caption here reflects. The "Willis" is Bruce Willis. And he gets a $5 million-plus arbitration award against a producer, but it only survives against the company. Good luck collecting on that. Although the arbitrator held that the wealthy individual behind the company was also liable, we'll need a court to decide that issue.
So no immediately forthcoming check for Mr. Willis. The exact opposite of Yippie ki-yay for him.