Hi just add this code in your theme functions.php
add_action('init', 'mydomain_plugin_checks');
function mydomain_plugin_checks(){
if ( class_exists('BanHammer') ) {
add_filter('woocommerce_registration_errors', 'woocommerce_banhammer_validation', 10, 3 );
}
}
function woocommerce_banhammer_validation( $validation_errors, $username, $email ) {
if( (new BanHammer)->banhammer_drop( $username, $email, $validation_errors ) )
return new WP_Error( 'registration-error-bad-email', (new BanHammer)->options['message'] );
return $validation_errors;
}