The GP putter is 100% legal for any golf tournament in the WORLD.
THE GP putter “Conforms with USGA Rules” also with the R&A.
This is a email from Mike Schy who is Bryson Dechambeau golf instructor.
From: schygolf <email@example.com>
Date: Sun, Feb 2, 2014 at 10:19 AM
Subject: Mike schy
To: PR Dionne Inc <firstname.lastname@example.org>
Not sure you are tracking Bryson but he is leading the jones cup using your GP putter.
Hoping for a a great finish! !