Template:M summ GMSLA 27.3
Does an exchange of emails count as confirmation by “electronic messages on an electronic messaging system”? you might think so, but the judgment in Greenclose v National Westminster Bank plc — albeit about the ISDA Master Agreement might give you a different view.
Much of the meat and drink of the commercial terms of a 2010 GMSLA — dividend rates, pricing schedules, individual transaction terms — take place outside the four corners of the master agreement itself, so a no oral modification clause seems a little ripe, unless you construe it narrowly to refer only to the terms encoded in the master agreement and its schedules, I guess.