Groundhog246 once bubbled...
Legally speaking, NO. In retail terms your course is a "product" and you don't have the legal right to refuse to sell that "product" to anyone (exception for gear, you CAN require a C card, same as a card renatl company can require proof you have a drivers license). Now, you can ask them to establish they're physically fit enough, require a medical clearance, etc., but you can't unilaterally refuse to provide the course.
I guess I can't argue the letter of the law but I'll give a silver dollar to the person that can force me to take a student I don't want. My class isn't a product it's a service and I'll provide it when, where and to whome I choose.
Just like the local bar I reserve the right not to serve.
I just turned down a student because she was 11 years old. The agency says that's old enough. I say I don't take students that yong.