I was up ice fishing in Canada last weekend. Fishing was a bit slow so stories were told.
My brother-in-law told me that his buddy went to a FITASC event and, while wearing shorts and flip flops, stepped up to the line. He was immediately DQed. He was told they wear long pants and shoes. His entry fee was not refunded.
I was at a training event for Scheel's. We were being shown a video from the manufacturer of the item we were training on starring Lena Mikulec. In the video she enters an indoor range and is wearing sandals. She proceeds to stop to her bay and shoots wearing the sandals.
I thought OGC had a prohibition against sandals or open toed shoes. I would never think of shooting with that kind of footwear.