marry_on_realm_law

marry_on_realm_law = {
	if = {
		limit = {
			$SPOUSE_1$ = { is_ruler = yes }
			$SPOUSE_1$ = {
				OR = {
					has_realm_law = male_only_law
					has_realm_law = male_preference_law
				}
			}
		}
		$SPOUSE_1$ = { marry = $SPOUSE_2$ }
	}
	else_if = {
		limit = {
			$SPOUSE_1$ = { is_ruler = no }
			$SPOUSE_1$.liege ?= {
				OR = {
					has_realm_law = male_only_law
					has_realm_law = male_preference_law
				}
			}
		}
		$SPOUSE_1$ = { marry = $SPOUSE_2$ }
	}
	else_if = {
		limit = {
			$SPOUSE_1$ = { is_ruler = yes }
			$SPOUSE_1$ = {
				OR = {
					has_realm_law = female_only_law
					has_realm_law = female_preference_law
				}
			}
		}
		$SPOUSE_1$ = { marry_matrilineal = $SPOUSE_2$ }
	}
	else_if = {
		limit = {
			$SPOUSE_1$ = { is_ruler = no }
			$SPOUSE_1$.liege ?= {
				OR = {
					has_realm_law = female_only_law
					has_realm_law = female_preference_law
				}
			}
		}
		$SPOUSE_1$ = { marry_matrilineal = $SPOUSE_2$ }
	}
	else = {
		marry_spouse_1_dominant = {
			SPOUSE_1 = $SPOUSE_1$
			SPOUSE_2 = $SPOUSE_2$
		}
	}
}

As written in game/common/scripted_effects/00_marriage_effects.txt.