Is it permissible for a Muslim man to marry a Muslim woman who has no guardian (wali), given the difficulty of obtaining the young man's embassy's approval to legalize the marriage in a non-Muslim country? And what is the ruling on the marriage if it takes place without a guardian, with only two witnesses and public declaration?

If a woman's Islam is known, but she has no Muslim guardian, such as her family, or the ruler, or his deputy, or Islamic centers, then a man from among the general Muslim populace may marry her off in the presence of two just witnesses. This is what Ahmad ibn Hanbal's statement indicates. So, if a Muslim man undertakes the marriage contract with her acceptance and the presence of witnesses, there is no legal impediment according to Sharia (definition). Nevertheless, it is not advisable if official documentation is not possible, due to the potential for legal accountability or the loss of rights that may result.