What is the ruling of Islamic law regarding the marriage of a Muslim woman residing in an Arab country without a guardian, when her father refuses to marry her to an Arab Muslim due to a difference in nationality?

A woman's guardian should marry his daughter to someone whose religious commitment and character he approves of, and nationality differences should not be an impediment. If the father insists on refusing, and the girl fears falling into temptation, she may refer her case to a Muslim judge to marry her to a suitable match.