Mickelson's wedge | Golf Monthly

This has a relevant quote or two. I think it's from The Canadian Press :

After a dispute with USGA, Phil Mickelson goes with square-groove Ping wedge
By Doug Ferguson (CP) – 3 days ago

SAN DIEGO — Phil Mickelson has been one of the strongest critics of the USGA's new regulation that bans square grooves, so it was not surprising that he became the latest player to put the Ping-Eye 2 lob wedge in his bag.

The Ping wedge, which has square grooves, is not affected in this new era of V-shaped grooves because of a lawsuit Ping filed against the USGA that was settled 20 years ago. Under the settlement, any Ping-Eye 2 made before April 1, 1990, is allowed.

Some have said players using the Ping wedges are violating the spirit of the rule.

Mickelson doesn't buy it.

"I've sent in grooves that are legal but have not been approved for play," he said. "And I feel like the Eye-2 grooves are not legal, or don't conform, but they are approved for play. And after talking about it to the tour and the USGA, the only thing that matters is, 'Are they approved for play?'

"So I don't feel that there's any problem if I were to play those clubs or if anybody else were," Mickelson said. "All that matters is that it is OK under the Rules of Golf."

Mickelson isn't alone.

John Daly has been collecting Ping-Eye 2 wedges over the last few months and used them in Honolulu. Ditto for Dean Wilson.

Among other players using the Ping wedges are Brad Adamonis and Hunter Mahan, whose caddie found the beryllium copper wedge that Mahan is using at Torrey Pines.

Mickelson had several wedges from when he played Ping clubs at Arizona State as a freshman. He is only using the lob wedge, which he had Callaway bend from a 60-degree to a 64-degree club.

Lefty said he believes he will pick up even more spin this year in his other wedges because he said Callaway was "fractionally more aggressive" with the V-grooves, and he is using a slightly softer ball.

Nothing to do with loopholes.

Golf is the most 'rules is rules' game out there. He's been open and discussed it with the relevant bodies, so where's the problem ?