There is no "legal limit." The USGA publishes suggestions for clubs, but they aren't rules, and they certainly don't imposes any restrictions on the national championship.McIlory for sure
5 yards is the legal limit for pin location in relation to the edge of the green, so I'm now sure how they're getting away with 3 and 4 yards.
9 greens with 5 or less...
Rule 16
Requirements for Hole Location on the Putting Green
Q.What are the requirements for establishing a hole location on the putting green?
A.The USGA frequently receives requests for guidelines with respect to selection of hole locations on the putting greens, particularly during competitions. There are no rules regarding hole locations, so there is no such thing as an "illegal" hole location.