Ok this question: How do I do multiple has_and_belongs_to_many associations between the same two classes? gave me a strategy to rename my relation in the Person model. So now I have:
class Person < ActiveRecord::Base
has_and_belongs_to_many :staffed_events, :join_table => 'events_staff', :class_name => 'Event'
end
And my filter is filter :staffed_events