Final answer:
The degree of regional integration being described is a free trade area, where participating countries remove trade barriers between themselves but maintain their own trade policy with non-members.
Step-by-step explanation:
The degree of regional integration being described in this scenario is a free trade area.
In a free trade area, participating countries remove trade barriers (such as tariffs and quotas) between themselves, allowing for the free flow of goods and services. However, each country maintains its own trade policy with non-members, which means they can impose trade restrictions or regulations on imports from outside the free trade area.
In the case of Valyria and Winterfell, both nations have agreed to eliminate trade barriers between them, but they have not reached an agreement to create a common external trade policy towards non-members. Therefore, they are considered to have a free trade area.