The rabbinical courts exist for sorting out religious issues, such as religious marriages and divorces of Jewish citizens. Judaism is not even special-cased: «Such courts exist for the recognized religious communities in Israel, including Muslim courts, Christian courts, and Jewish Rabbinical courts.» (Wikipedia).

The Basic Laws, which sort of comprise the makeshift constitution of Israel, don't seem to make any religious references, but rather refer to the founding UN principles like human rights.

My apartment rental agreement had a clause all "all disagreements are to be resolved in rabbinical court". Reach of the religious courts is unlimited.

Even civil courts are allowed to refer to holy texts if the law is not clear.