systems generally do not recognize the agunah status, but an agunah would not typically pursue a second marriage, since her first marriage is still valid according to halakha, therefore any other sexual relationships would constitute adultery from her first husband. Furthermore, according to halakha, any children born by an agunah are considered mamzerim (bastards). The earliest prenuptial agreement for the prevention of get-refusal was developed and accepted by the Rabbinical Council of Morocco on 16 December 1953. The prenuptial agreement gained further approbation in 1981 from Rabbi Shalom Messas, chief rabbi of Jerusalem. Following Rabbi Messas' involvement, the Rabbinical Council of America actively pursued this issue. The latest in a series of RCA resolutions—"that since there is a significant agunah problem in America and throughout the Jewish world, no rabbi should officiate at a wedding where a proper prenuptial agreement on get has not been executed"—was passed on 18 May 2006. In 2012 the International Rabbinic Fellowship (IRF), an international organization of (as of 2012) 150 Modern Orthodox rabbis, passed a resolution saying that, "IRF Rabbis may not officiate at a wedding unless the couple has signed a halachic prenuptial agreement. IRF Rabbis are further encouraged to participate ritually only in weddings in which the couple has signed a halachic prenuptial agreement. Ritual participation includes but is not limited to reading the ketubah, serving as a witness, and making one of the sheva berachot." This makes the IRF the only Orthodox rabbinical organization in the world to require its members to use a halachic pre-nuptial agreement in any wedding at which they officiate. Beginning in the 1950s, some Conservative rabbis have used the Lieberman clause, named for Talmudic scholar and Jewish Theological Seminary (JTS) professor Saul Lieberman, in the ketuba, requiring that a get be granted if a civil divorce is ever issued. Most Orthodox rabbis have rejected the Lieberman clause, although leaders of the Conservative movement claim that the original intent was to find a solution that could be used by Orthodox and Conservative rabbis alike, and that leaders of Orthodox Judaism's Rabbinical Council of America, and respected Orthodox rabbis, including Joseph B. Soloveitchik, supposedly recognized the clause as valid. Later, because some civil courts viewed the enforcement of a religious document as a violation of the constitutional principle of the separation of church and state, Conservative rabbis began to require couples to sign a separate letter, stating that