Enable IP Geolocation in your Cloudflare panel – it should be in the Network tab.

The country code will come in HTTP_CF_IPCOUNTRY header.

Now we can add a before_action filter to block or redirect the users from a specific country (in the example below we redirect all EU countries… because who has the time to figure out GDPR):

class ApplicationController < ActionController::Base
  before_action :block_gdpr_countries

  GDPR_COUNTRIES = [
    'BE', 'EL', 'LT', 'PT',
    'BG', 'ES', 'LU', 'RO',
    'CZ', 'FR', 'HU', 'SI',
    'DK', 'HR', 'MT', 'SK',
    'DE', 'IT', 'NL', 'FI',
    'EE', 'CY', 'AT', 'SE',
    'IE', 'LV', 'PL', 'UK'
  ]

  def block_gdpr_countries
    return unless GDPR_COUNTRIES.include?(request.env['HTTP_CF_IPCOUNTRY'])
    redirect_to gdpr_path
  end
end

Remember to skip this action in the corresponding controller (in our case gdpr_controller) if you use a redirect:

skip_before_action :block_gdpr_countries