Father's consent required for marriage?

From a Fatwa of a well-known and well-respected Saudi cleric, Sheikh Aziz bin Baz:

...The father must seek her permission if she is nine years of age or above. Similarly, her other guardians may not marry her off except by her permission. This is obligatory upon all of them. If o­ne is married without permission, then the marriage is not valid. This is because o­ne of the conditions of the marriage is that both partners accept the marriage. If she is married without her permission, by threat or coercion, then the marriage is not valid. The o­nly exception is in the case of the father and his daughter who is less than nine years of age. There is no harm if he gets her married while she is less than nine years old, according to the correct opinion. This is based o­n the Messenger of Allah (peace be upon him) marrying Aisha without her consent when she was less than nine years old, as is stated in authentic Hadith. However, if she is nine years old or more, she cannot be married, even by her father, except with her consent....