from what i know Diplomate are not allowed to carry guns in another country diplomats can carry/own weapons for personal protection. Small hand gun, etc. They can not flaunt weapons or carry weapons that are illegal in an area. you are looking to buy MP5 which is automatic gun no one is allowd to by automatic guns in pakistan
They are also allowed armed bodyguards, normally military solders from their "home" country. if the situation demands it.
Embassy are also protected by armed guards and gun/weapons in a diplomats car are allowed as well.
It depends again on the situation and host country.
Civilian gun licenses in Pakistan vary considerably in terms of region and class of firearm. Local police agencies can issue permits for submachine guns that are only legal in the state in which they are issued, although a licence issued by the Prime Minister will allow the gun in question to be transported anywhere in the country. There are complaints that the licensing process has become too politicized
hope that helped