Quoting Andrew Jotischky in Antisemitism and Islamophobia in Europe: A Shared Story?, page 27:

The consensus among historians of the Crusader States has tended to be that in terms of legal status, distinctions were made not according to religion or language group, but according to the political fact of conquest: one was either a Frank or a non-Frank.¹⁰

However, the earliest laws promulgated in the kingdom of Jerusalem, the Concordat of Nablus (1120), overlaid this state of affairs with a degree of religious segregation by prohibiting sexual unions between Franks and Muslims. Muslim women who consented to sex with a Frank were to have their noses cut off; Frankish men who raped Muslim women were to be castrated; while Frankish women who had consensual sex with Muslim men were to be treated as adulterers, and therefore liable to death.

These laws, the penalties for which are taken from Byzantine precedents rather than contemporary Western laws, demonstrate the desire to keep Franks and Muslims in separate social spheres. In the concern they betrayed to ensure that there could be no mixed biological issue from such unions, moreover, they reinforced legal separation on grounds of ethnicity.¹¹

(Emphasis added.)