Send a "403 error" through Elgg

I have a antispam plugin and I am developing a new version that will block the registration form only to blacklisted ips. In my beta version, I use the php function die() in a view extendind the register view, so blacklisted ips see only a blank page.

Is it possible send a http header with a 403 response? I think that in the register view, elgg still sent the headers. What can I do? Hooks the "start.php" or something like this? Clear the php bufeer? Or just use die() function and forget about it?