All things are possible, it's just a question of how much work you want to put into it.

is there a way to detect visitors who are (probably) in Pakistan (like, is there a specific block of IPs that is assigned to Pakistan)

http://www.find-ip-address.org/ip-country/

redirect them to a page explaining that you'd rather not risk getting a death sentence from Pakistan, so you are not willing to serve content in that jurisdiction?

http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html

memfrob(3)