Foreigners cannot apply for permanent residency, though a specialized Premium Residency visa became available in 2019. Only Muslims can become Saudi citizens. Foreigners who have resided in the kingdom and hold degrees in various scientific fields may apply for Saudi citizenship, and exception made for Palestinians who are excluded unless married to a male Saudi national, because of Arab League instructions barring the Arab states from granting them citizenship. Saudi Arabia is not a signatory to the 1951 UN Refugee Convention.