location /admin {
    error_page 403 = @deny; // Return forbidden and redirect
    allow 127.0.0.1;
    allow 192.168.0.1;
    deny all;
    try_files $uri $uri/ /index.php?$query_string; // Important for PHP rewrite cond ej (index.php/admin)
}

location @deny {
    return 301 http://example.com; // The redirect URL
}