Currently anyone can join an event. While this should remain for the vast majority there are many events and races which would benefit from allowing the organisers to pre-select or qualify entrants.
For example a women’s race could be open to women only. A Masters race could be open to people in certain age groups. The Final of a race series could be open only to the winners of previous races.
This is not about excluding or banning individuals. The organiser would set objective criteria and anyone meeting them is permitted to take part. The organiser would then have to create a set of qualified users.