Is the jurisprudential maxim, "That which has more harms than benefits is unlawful," sound, and is the marriage of a non-Gulf national to a Gulf national unlawful based on it?

The guardian (wali al-amr) has the right to enact laws prohibiting his citizens from marrying non-citizens, if this entails a benefit or averts a harm. The assessment of this matter rests with people of knowledge and experience. The citizens must comply with this law, and this does not contradict the principle of kafa'ah (suitability) in marriage based on religion.