When I was a pledge (because it was the last semester we were allowed to be called "pledges" before the NPC rule took effect

), our Code of Standards was one of the first things we reviewed during our Pledge Meetings. Everything was simply stated in the Code of Standards -- attire, punctuality, and attitude and behavior. Though we weren't yet initiated members, we were still representatives of the sorority.
There was no "ifs, ands, or buts" about the Code of Standards. Each pledge was expected adhere to it whether or not they were in the presence of the Sisters or other Greeks. There was a sense of trust between Pledges and Sisters because we knew how we were supposed to be behave.
But--in the event we failed to represent AGD according to the code, we had "THE SHOULDER TAP", a discreet way of telling a sister "you shouldn't be doing that". You never wanted to receive one of those, and if you did, you probably felt bad about getting one!
GLOs have the right to moderate the way their new members act and represent them and at the same time new members have a choice to either accept this or not. I feel that accepting this tells your chapter "I really want to be a part of XYZ and I respect the ideals XYZ stands for."