Cellphones are not allowed.
Unlike the PGA Tour, which since last year has permitted the use of cellphones at tournament sites, the USGA has yet to go that far, at least where the U.S. Open is concerned.
But it's not necessarily for the reasons that bothered Mickelson and have been an issue at several tour sites this year.
"We're going to allow them for the [U.S.] Women's Open, so we're not opposed to it,'' said USGA executive director Mike Davis while watching Tiger Woods play a practice round Monday at the Olympic Club. "You've been to enough big sporting events to know, when you start to congregate 40, 50, 60,000 people, all of a sudden nobody's cellphones work.
"We need to get more comfortable from a technology side. It's one thing to do it at the Women's Open when you don't have near the crowds. We didn't want a scenario where we're promoting it, people bring them, and all of a sudden they don't work. The NFL has issues with it. This is something that will correct itself in time.''
Mickelson withdrew after a first-round 79 two weeks ago at the Memorial, publicly citing mental fatigue. But also at issue was the number of distractions due to spectators taking photos with their phones. While taking pictures or video is prohibited, the ban is widely ignored by spectators and difficult to enforce. And if a cellphone camera is not turned on silent, it makes the same noise as a regular camera when a picture is taken.
"The bigger the galleries are, obviously the more people you have, and now where these people can use them we don't mind it, it's just put it on silent,'' Woods said at The Players Championship last month. "It's not that hard. But they don't. And it's gotten [so that] it can cost guys tournaments, because a shot on Thursday is the same as a shot on Sunday. So it's one of the difficult things about it.''
Davis said the USGA is also concerned about the distractions -- although it's not likely to be an issue this week. Spectators must pass through metal detectors at entrances.
"It's a balance,'' Davis said. "We are worried about that. But we want to have a good spectator experience, too. It seems to me you can probably manage that if your gallery marshals do a good job and you're proactive."
Bob Harig covers golf for ESPN.com. He can be reached at BobHarig@gmail.com.