From the Mazdamotorsports website:
To join, youll need to meet the following requirements:
*Be located in the United States, Canada, or Mexico.
*Have a valid membership with a sanctioning body/organization approved by Mazda (e.g., Sports Car Club of America SCCA; National Auto Sport Association NASA, etc.) for questions, call 800.435.2508. Ensure you can upload your membership card as a PDF or URL link from a non-password protected site.
*Either be building a Mazda race car for competition or have competed in one sanctioned/organized/off-highway event approved by Mazda within 12 months.