י רַבֵּנוּ גֵּרְשֹׁם הֶחֱרִים עַל הַנּוֹשֵׂא עַל אִשְׁתּוֹ; אֲבָל בִּיבָמָה לֹא הֶחֱרִים. וְכֵן בַּאֲרוּסָה. הַגָּה: אִם אֵינוֹ רוֹצֶה לִכְנֹס אֶלָּא לִפְטֹר (מַהֲרִי"ק שֹׁרֶשׁ ק"א). וְהוּא הַדִּין בְּכָל מָקוֹם שֶׁיֵּשׁ דִּחוּי מִצְוָה, כְּגוֹן שֶׁשָּׁהָה עִם אִשְׁתּוֹ עֶשֶׂר שָׁנִים וְלֹא יָלְדָה (מָרְדְּכַי פֶּרֶק הַחוֹלֵץ רַשְׁבָּ"א סִימָן ר"פ וּמהר"ם פַּדָּוואָה סִי' י"ט). אָמְנָם יֵשׁ חוֹלְקִים וּסְבִירָא לְהוּ דְּחֵרֶם רַבֵּנוּ גֵּרְשֹׁם נוֹהֵג אֲפִלּוּ בִּמְקוֹם מִצְוָה וַאֲפִלּוּ בִּמְקוֹם יִבּוּם, וְצָרִיךְ לַחֲלֹץ (הַגָּהַת מָרְדְּכַי דִּיבָמוֹת וְהַגָּהוֹת מָרְדְּכַי דִּכְתֻבּוֹת וְכֵּן כָּתַב נ"י פֶּרֶק הַחוֹלֵץ). וּבְמָקוֹם שֶׁאֵין הָרִאשׁוֹנָה בַּת גֵּרוּשִׁין, כְּגוֹן שֶׁנִּשְׁתַּטֵּית אוֹ שֶׁהוּא מִן הַדִּין לְגָרְשָׁהּ וְאֵינָהּ רוֹצָה לִקַּח גֵּט מִמֶּנּוּ, יֵשׁ לְהָקֵל לְהַתִּיר לוֹ לִשָּׂא אַחֶרֶת (כֵּן מַשְׁמַע בִּתְשׁוּבַת הָרַשְׁבָּ"א). וְכָל שֶׁכֵּן אִם הִיא אֲרוּסָה וְאֵינָהּ רוֹצָה לְהִנָּשֵׂא לוֹ אוֹ לִפְטֹר מִמֶּנּוּ. וְלֹא פָּשְׁטָה תַּקָּנָתוֹ בְּכָל הָאֲרָצוֹת. הַגָּה: וְדַוְקָא בְּמָקוֹם שֶׁיָּדוּעַ שֶׁלֹּא פָּשְׁטָה תַּקָּנָתוֹ, אֲבָל מִן הַסְּתָם נוֹהֵג בְּכָל מָקוֹם (תְּשׁוּבַת ר"י מִינְץ סִי' ק"י). וְעַיֵּן בְּיוֹרֶה דֵעָה סִי' רכ"ח אִם הָלַךְ מִמָּקוֹם שֶׁנָּהֲגוּ לְהַחֲמִיר לְמָקוֹם שֶׁנָּהֲגוּ לְהָקֵל. וְלֹא הֶחֱרִים אֶלָּא עַד סוֹף הָאֶלֶף הַחֲמִישִׁי. הַגָּה: וּמִכָּל מָקוֹם בְּכָל מְדִינוֹת אֵלּוּ הַתַּקָּנָה וְהַמִּנְהָג בִּמְקוֹמוֹ עוֹמֵד, וְאֵין נוֹשְׂאִין שְׁתֵּי נָשִׁים, וְכוֹפִין בַּחֲרָמוֹת וְנִדּוּיִין מִי שֶׁעוֹבֵר וְנוֹשֵׂא ב' נָשִׁים לְגָרֵשׁ אַחַת מֵהֶן. וְיֵשׁ אוֹמְרִים דְּבַזְּמַן הַזֶּה אֵין לָכֹף מִי שֶׁעָבַר חֵרֶם רַבֵּנוּ גֵּרְשֹׁם (ב"י סִי' ע"ו), מֵאַחַר שֶׁכְּבָר נִשְׁלַם אֶלֶף הַחֲמִישִׁי (שָׁם בְּשֵׁם מַהֲרִי"ק), וְאֵין נוֹהֲגִין כֵּן. יֵשׁ אוֹמְרִים מִי שֶׁנִשְׁתַּמְּדָה אִשְׁתּוֹ, מְזַכֶּה לָהּ גֵּט עַל יְדֵי אַחֵר וְנוֹשֵׂא אַחֶרֶת, וְכֵן נוֹהֲגִין בִּקְצָת מְקוֹמוֹת (פִּסְקֵי מהרא"י סִי' רנ"ו). וּבְמָקוֹם שֶׁאֵין מִנְהָג אֵין לְהַחֲמִיר וּמֻתָּר לִשָּׂא אַחֶרֶת בְּלֹא גֵּרוּשֵׁי הָרִאשׁוֹנָה (שָׁם מִנְהֲגֵי רַיְנוּ"ס):
10 RABBEINU GERSHOM DECREED CHEREM for one who marries [another] in addition to his wife, but in regards to a Leverite marriage, he did not decree cherem, and such is also the case with a betrothed woman. Rema: If he doesn't want to marry another, but rather to release her, and this is the rule in any place that a mitzvah would be delayed -- for instance, if he was married to his wife for ten years and she didn't give birth (Mordechai, Perek 'Hacholetz' Rashba siman 280 and Maharam Padua Siman 19). However there are those who disagree and say that Rabbeinu Gershom's decree applies even in a case in which a mitzvah is involved, and even in the case of a Levirite marriage, and one must do Chalitza (see Hagahot Mordechai in Yebamot and Ketubot). And in the case where the first wife is not easily divorceable, e.g. she became mentally infirmed, or the husband is legally allowed to divorce her but she won't accept a Get from him, one should be more lenient and allow him to marry another (see Rashb"a). And this case if she is betrothed and neither wants to marry him nor to be released from the betrothal. AND HIS [Rabbeinu Gershom's] DECREE was not unilaterally accepted in all the lands. Rema: Particularly in a plce where it is known that his decree wasn't unilaterally accepted, but basically it applies everywhere. See Section 14 Siman 228 for what one should do if he moved from a place where they are stringent on this ruling to a place where they are more lenient. AND HE ONLY EXTENDED THE DECREE until the end of the 5th centure (i.e. 500 years from when he said it). Rema: In any case, in all of these lands, the decree and the custom stand in their place, and we don't marry two women, and this is a punishable offense, and we force someone who did marry two wives to divorce one of them. And there are those who say that in this day and age, we shouldn't punish one who disobeys this decree because the fifth century [since it was declared] has already passed [and so it is expired], but this is not our custom. There are those who say that one whose wife refuses to accept a Get, he can serve it to her through someone else and then marry another, and this is the custom in some places. And in a place where this is not the custom, one should not be stringent, and a man may marry a second [wife] without divorcing the first.