"The confluence of golf and an insider trading investigation is hardly new."

Ben Protess and Matthew Goldstein file a follow-up NY Times story on the Icahn-Walters-Mickelson investigation and put a circumstantial case together that sounds like it's lacking the necessary evidence to prosecute.

The recent move on Mickelson at the Memorial appears to have been an effort to get him to snitch on Billy Walters due to insufficient evidence.

As one of America’s most popular athletes, Mr. Mickelson had much to lose under the glare of the government’s spotlight.

But when the F.B.I. approached Mr. Mickelson — first pulling him off a plane at Teterboro Airport in New Jersey last year, the people said, and then confronting him on Thursday at a golf tournament in Ohio — Mr. Mickelson had little to offer. In the airport discussion last year, which lasted no more than an hour, the people said, Mr. Mickelson pledged to cooperate but explained that he did not know Mr. Icahn and had no clue that the stock tips might have been improper. On Thursday, Mr. Mickelson said, he instructed F.B.I. agents to “speak to my lawyers.”

And there is this:

A year after the 2011 Clorox trades, Mr. Walters and Mr. Mickelson placed trades in Dean Foods, the people briefed on the matter said, just before the food and beverage company announced its quarterly earnings and a public stock offering for a subsidiary. The authorities, who have not found any connection between Mr. Icahn and the Dean Foods trading, are investigating whether Mr. Walters had a source inside the company itself.

For the Clorox trades, Mr. Walters provides authorities with a possible link between Mr. Icahn and Mr. Mickelson. Mr. Icahn, a frequent visitor to Las Vegas with a number of business interests there, acknowledges knowing Mr. Walters but says he has no connection to Mr. Mickelson. Mr. Walters, for his part, has crossed paths with Mr. Mickelson at golf tournaments.

“With this breaking in the media, the government’s next step will likely be sending out grand jury subpoenas to the parties for all documents, emails and text messages,” said Reed Brodsky, a partner with Gibson Dunn & Crutcher and a former federal prosecutor.

The story also looks at some past insider-trading cases related to golf.