Is it permissible for the wife to prevent her husband's parents from seeing their grandchildren, knowing that the husband is an expatriate and has authorized his father to see his children on his behalf?

It is not permissible for a woman to prevent her children's grandparents from seeing them, as this constitutes cutting off kinship ties. The right of the grandfather and grandmother to see their grandchildren is established by Islamic law and does not require the father's authorization.