have their Cal South issued Referee ID cards with name and picture in their possession
You MUST be currently registered as a USSF referee (up-to-date) and have your risk management completed if you are over age 18. Also you will need the ID Card to officiate any games in Presidio Soccer League and/or any related tournaments.
Member league's contract directly with the Referee Associations of their choice. Associations are required to use currently registered U.S. Soccer Federation referees and listed as "Approved" on the CalSouth website: