Is it permissible to marry a Muslim woman whose polytheistic and atheistic parents reject this marriage, and can one of the Muslims assume guardianship over her for the marriage?

Guardianship of a disbeliever over a Muslim woman is not established, by the consensus of scholars. Therefore, none of the girl's family members can be her guardian as long as they are not Muslim. The Muslim ruler then becomes her guardian, based on the saying of the Messenger of Allah, peace and blessings be upon him: "The ruler is the guardian of whoever has no guardian." If there is no Muslim ruler in her country, she is permitted to appoint a Muslim man to conduct her marriage.