"He's focusing on an 'inducement to infringe,' " said Paul Lesko, a partner at SimmonsCooper LLC in St. Louis and head of the law firm's intellectual property group. " 'Actively encouraged' -- that's the key phrase in Rubin's remarks there.

"Inducement to infringe is statutory for patents, and Rubin's trying to bring that to the copyright world," said Lesko. "He's trying to use Grokster to support some of Microsoft's claims against Google."

In the 2005 Grokster decision (officially MGM Studios Inc. v. Grokster Ltd.) by the U.S. Supreme Court, the concept of induced infringement -- that Grokster specifically encouraged copyright violations by its actions and business model -- was key, Lesko said. "Grokster was a peer-to-peer case, so Microsoft is drawing analogies between it and what Google is doing now," he said.

He wouldn't comment on whether Rubin might be laying the foundation for future legal action against Google.