Say a person draws up a last will and testament according to the laws of Country A and files it with his lawyer there. Then he moves to and takes up permanent residence Country B, and dies there. What happens to his estate? Do countries enter into treaties whereby they agree to recognize each other’s wills? Or would Country B simply hold that the person died without a valid will and dispose of his estate (or at least, whatever part of it was held in that country) in the default manner prescribed by its laws? To be safe, does a person need to draw up a separate will for each country in which he holds property?
The Hague Convention on the law applicable to succession to the estates of deceased persons and the Hague Convention on the conflicts of laws relating to the form of testamentary dispositions may be helpful here. If you click on “status table” on those pages, you’ll see what countries have signed up (or acceded or succeded), and whether they have accepted the convention in whole or in part.