I believe I heard from someone who certainly would know that Jim Vernon is really good on the Rules of Golf---really, really good. Those are the kinds of officials that go out with those kinds of groups, because "on course" they are very good, and that's what you want and need.
If I were out there in the US Open with a group like that (and I've been officiating for years) and Tiger or Phil asked me for a ruling, here's what I'd say:
"Well, what are the facts of this particular situation and what are you trying to accomplish, and are we talking about match play or stroke play here because the Rules application can be quite different, you know?"
