Notwithstanding the protestations to the contrary by these "Messianic Jews" or "Jews for Jesus", no person can believe in Jesus as the Messiah and concurrently be or remain Jewish (if he or she were Jewish to begin with). This rule was established and is adhered to by the Orthodox rabbis (and probably backed by the majority in the Conservative Movement) and was augmented by a ruling of the Israeli Supreme Court a few years ago.