Page 5 of the rulebook:
INEX MEMBERSHIPS (Member and Associate):
All competitors must have submitted an INEX application in order to be permitted to compete in any INEX-sanctioned event.
That says it all, no membership, no racing.
All fine and dandy Steve, but not being members, and not caring about points, they wont have to follow the rules either, and will affect people running for points. When you get wrecked by a non-member, it affects you