Sumptuary Law was the medieval legal practice of maintaining social order by regulating the outward display of wealth and station. Violating these laws, or “dressing above your station” could be a considerable infraction, although enforcement varied considerably throughout Europe and throughout Period.
In the SCA sumptuary laws are relatively simple, determining mostly what crowns and coronets can be worn, as well as restricting white belts and baldrics to the Order of the Chivalry. Restrictions of heraldic display, particularly of the badges of various orders and Peerages, also fall under the aegis of sumptuary law.
It is worth noting that many customary usages in the SCA, particularly the colours of belts for squires, apprentices and proteges, are not officially covered by SCA Sumptuary Law but instead by the laws and customs of individual Kingdoms.
Note that in Ealdormere, there are very few true sumptuary laws. Instead, Ealdormere has customs, largely in keeping with our time as a vassal of the Middle Kingdom.