Obviously you can deny admission to someone who does not meet the required (nondiscriminatory) qualifications. You can get into trouble if you are large enough and open enough to be considered a public accommodation and the applicant claims you have discriminated against a member of a protected class. Trade associations occasionally get into trouble for alleged antitrust violation if they deny membership to a qualified applicant, but that argument is not likely to be applied to a sports club. Your biggest issue may be a public relations issue if you deny admission to otherwise qualified applicants. It may not be popular with some existing members or the broader public.