If You have Gun Tag You are allowed to use rifle or shotgun.
If You Do NOT have Gun Tag You are allowed to use only pistol or knife.
And gun must be covered so You can not use it immediately.
Gun Tags is lootable item (Game item)
Stalker Loner kills Freedom Player.
In 5 minute period he can come and take his Gun Tag. From the same moment Stalker can use his Gun because he have Gun Tag. Freedom player after respawn Can NOT use his gun because he does not have Gun Tag.
Gun Tag must be worn on neck.
It must be visible
Gun Tag can be acquired in following ways:
Simply found in The Zone
On Dead people (You can always help them to become dead)
Bought from traders, NPC, Military and so on.