The 1997 SASS rule book has no rules for boots other than in the outlawed section.
Outlawed: Tennis, running, jogging, or aerobics shoes ( Indian moccasins work well for relaxing after a long day in boots.)
2016 rule book:
Classic cowboy/ girl: Boots are required and must be of traditional design with non-grip enhancing (i.e. ―NO Lug‖) soles. Moccasins are not allowed.
"B" western: Boots are required and must be of traditional design and embellished with fancy stitching, multi-color fancy design, conchos or spots. Soles must be non-grip enhancing (i.e., ―NO Lug‖) soles. Lace up boots and moccasins are not allowed.
Outlawed: All types of athletic shoes or combat boots, no matter the material from which they are constructed.