Well, USSF under its 100% rule protects the rights of member clubs to dual affiliate under such USSF-sanctioned organizations as US Youth Soccer (USYSA), US Club Soccer (USCS), and other organizations of USSF (i.e. AYSO). There is nothing WYS can do that would be upheld by USSF in a grievance proceeding that would either prevent dual affiliation or discrimination by WYS based on dual affiliation since it is protected by WYS's parent's (USYSA) parent organization (USSF).
Here's what USSF 603, Interplay, Section 1, popularly but not technically termed the "100% rule", actually says:
Section 1. One Organization Member may not require that all of the players, coaches, teams, and administrators of another Organization Member (who have been registered with, and fees paid to, the Federation as required by section 1 of Bylaw 212) be registered with the first Organization Member as a condition for only some of those players, coaches, teams, or administrators participating in the activities of the first Organization Member. The first Organization Member may require registration of only those players, coaches, teams, and administrators of the other Organization Member that actually participate in the activities of the first Organization Member. Those players, coaches, teams, and administrators of the other Organization Member registering with the first Organization Member shall comply with all of
the regular registration requirements of the first Organization Member.
Between a reading of this bylaw and policy statement 212-1, "Participation in Affilated Organizations", one might conclude that dual affiliation is a "protected right", but it's not a right by the plain language contained therein. It would have to be inferred. In grievance proceedings, the language is interpreted narrowly.