From The Nation:
In most countries, a woman in her mid-20s is legally an adult. And in most countries, foreigners are free to leave when they like. In its flagrant rejection of these two principles, Saudi Arabia is unique, and that is a big problem for 24-year-old Nazia Quazi. For more than two years Nazia, an IT specialist who graduated from the University of Ottawa and holds dual Canadian-Indian citizenship, has been trying to leave Riyadh and go home to Canada. Her troubles began on November 23, 2007, when she entered Saudi Arabia with her parents on a visitor's visa. In Saudi Arabia, foreign visitors must have a sponsor, a local man who handles their paperwork. Nazia's sponsor is her father, Quazi Malik Abdul Gaffar, an Indian citizen who has worked in Saudi Arabia for many years. At some point Nazia's father clandestinely switched her visitor's visa to a more permanent visa–one that requires that he, as her sponsor, approve her exit visa. This he refuses to do. No exit visa, no departure. Worse, Nazia says he has confiscated both her Indian and Canadian passports and all her identity documents–driver's license, health card, credit cards and so on–and refuses to return them. She is trapped.
Nazia's father is not only her sponsor; he is also her mahram, or guardian, the male relative who in the Saudi system controls nearly every moment of a woman's life. As detailed in a 2008 Human Rights Watch report, under this system a woman must seek her mahram's permission to go to school, travel abroad, marry, open a bank account, hold a job, rent an apartment or even have elective surgery. (In June the Saudi government told the UN Human Rights Council that the guardianship system no longer exists, but HRW and the Saudi newspaper Al-Watan confirm that it does.) In effect, it makes women children for life–there are middle-aged Saudi women who are under the legal control of their own sons. Nazia's father thus has not only been able to force his daughter, through the sponsorship system, to remain in Riyadh; as her mahram he has total control of her life while she is there–even though neither Nazia nor her father is a Saudi citizen.
More here. (Note: Thanks to my friend Professor C.M. Naim)