function johnproject_save_check_shipping( $post_id ) {

    if(!is_valid_shipping_destination($_POST["attribute_values"][1][0], $_POST["attribute_values"][2][0]))
        $error = $WP_Error("broke","Your product does not qualify for shipping.  Please review your specifications carefully and try again.");

    return false

}
add_action( 'save_post', 'johnproject_save_check_shipping' );

function johnproject_presave_check_shipping( $data ) {

    if(!is_valid_shipping_destination($_POST["attribute_values"][1][0], $_POST["attribute_values"][2][0]))
        $error = $WP_Error("broke","Your product does not qualify for shipping.  Please review your specifications carefully and try again.");


    return $data;
}

add_filter( 'wp_insert_post_data', 'johnproject_presave_check_shipping' );

function is_valid_shipping_destination($productType,$productVariation)
{
    // for test purposes, always return false to see if errors are reported on product page
    return false;
}