WPA referees will now allow those who are 13 years old to register to become a certified US Soccer Federation Grassroots referee. You must be 13 y/o at the time of registration. You also need to obtain PA clearances. There is no need for a work permit but you will need to obtain one at
Referees should complete their SafeSport training through logging into their personal referee account in the learning center at https://learning.ussoccer.com/referee . There has been some issues with this training due to a data migration, but these issues are largely resolved. You can find further details at https://cms.ussdlc.com/safesport-transition-info-and-faqs/ which contains the most current guidance.