Would you duplicate the validation's regex, or reference a constant?

option_1.rb

class User
  field :username, :type => String

  validates :username, :format => { :with => /\A[[:print:] ]{3,20}\Z/ }
end

class ScoreCard
  belongs_to :user

  field :username, :type => String

  validates :username, :format => { :with => /\A[[:print:] ]{3,20}\Z/ }
end

option_2.rb

class User
  USERNAME_REGEX = /\A[[:print:] ]{3,20}\Z/

  field :username, :type => String

  validates :username, :format => { :with => USERNAME_REGEX }
end

class ScoreCard
  belongs_to :user

  field :username, :type => String

  validates :username, :format => { :with => User::USERNAME_REGEX }
end