On Friday, the Wall Street Journal and New York Times reported that federal authorities are investigating investor Carl Icahn, gambler William Walters and golf champion Phil Mickelson for insider trading. Investigators are examining a series of successful trades by Walters and Mickelson of shares of Clorox in 2011 shortly before Icahn announced an unsolicited (and ultimately unpursued) take-over bid for the company. FBI agents first questioned Mickelson about the trades a year ago, pulling him off a plane in New Jersey, then again last Thursday following his first round at the Memorial Tournament. Mickelson and Icahn both have denied even knowing each other. However, both know Walters and he may have been the link between the two.

Full disclosure: I’m a Phil Mickelson fan. Whether it’s his swashbuckling, go-for-broke style or the fact that we’ve eagled the same par four (mine was a fluke; his was Phil being Phil). He’s a risk-taker and with his aggressive game on the course comes both the good (think pine straw in 2010) and the bad (think Winged Foot in 2006). Perhaps that risk-taking has now gotten him into the deep rough with the SEC and DOJ.

Maybe, but maybe not. Even if Icahn passed information to Walters, who then passed it along to Mickelson, who then made a series of successful trades, liability is far from clear, particularly for a “downstream tippee” like Mickelson.

For there to be any insider trading liability, the tipper – Icahn – must have breached a fiduciary duty. Although Rule 14e-3 prohibits certain persons from disclosing or trading on information in connection with a tender offer, the rule applies only where the person making the offer has taken “substantial step” in making it. Icahn, who has no affiliation with Clorox, never made the offer. Icahn may have had a duty to his own investors to keep the proposed offer confidential, but the basis of such a duty is unclear and would likely turn on any non-disclosure requirements Icahn had with his investors.

But there are additional challenges in attaching liability to Mickelson. Even assuming that Icahn had a duty to his own investors, the government would need to demonstrate that “Phil the Thrill” knew or should have known that Icahn was breaching a fiduciary duty by making the a disclosure of non-public, material information. In addition, as we have blogged about previously, the government may also be required to demonstrate that Mickelson also knew or should have known that Icahn received a personal benefit from making the tip (also assuming that Icahn, in fact, received a personal benefit, an assumption that is far from clear).

That’s a lot of assumptions. So, ultimately, while Phil didn’t have the greatest week (or season) on the course, the government has an uphill fight in reaching him as a downstream tippee. In the meantime, Mickelson will chase that elusive U.S. Open victory at Pinehurst while the SEC and the DOJ continue to shoot for the pin as they aggressively pursue insider trading.