| From the 2008 Rules of Golf on USGA's website (pages 130-131 in the .pdf file of the Rules of Golf)
3. Grip (see Fig. VII)
The grip consists of material
added to the shaft to enable the
player to obtain a firm hold. The
grip must be fixed to the shaft,
must be straight and plain in
form, must extend to the end of
the shaft and must not be molded
for any part of the hands. if no
material is added, that portion of
the shaft designed to be held by
the player must be considered the
grip.
(i) for clubs other than putters
the grip must be circular
in cross-section, except
that a continuous, straight,
slightly raised rib may be
incorporated along the full
length of the grip, and a slightly indented spiral is permitted
on a wrapped grip or a replica of one.
(ii) A putter grip may have a non-circular cross-section,
provided the cross-section has no concavity, is symmetrical
and remains generally similar throughout the
length of the grip. (See Clause (v), below.)
(iii) The grip may be tapered but must not have any bulge
or waist. its cross-sectional dimensions measured in any
direction must not exceed 1.75 inches (44.45 mm).
(iv) for clubs other than putters the axis of the grip must
coincide with the axis of the shaft.
(v) A putter may have two grips, provided each is circular
in cross-section, the axis of each coincides with the
axis of the shaft, and they are separated by at least
1.5 inches (38 mm).
It looks like (iii) addresses the issue at hand -- it specifically states that the grip may indeed be tapered, but not have a bluge or rib or waist.  |