What is the ruling of Islamic law regarding a father forcing his daughter to marry her cousin despite her unwillingness, and his rejection of other suitors?

It is not permissible for a father to marry off his daughter to someone she does not wish to marry, for the woman's consent is a condition for the validity of the marriage contract. This is based on the Prophet's (peace be upon him) saying: "A non-virgin woman may not be married until she is consulted, and a virgin woman may not be married until her permission is sought." And her permission is her silence.

If the marriage contract is concluded without her consent, it is suspended until she ratifies it.

Furthermore, it is obligatory for the father not to prevent his daughter from marrying someone whose religiosity and character she approves of, provided he is a suitable match. Otherwise, he would be unjustly preventing her marriage, based on the Prophet's (peace be upon him) saying: "If there comes to you one whose religiosity and character you approve of, then marry him. If you do not do so, there will be tribulation on earth and widespread corruption."