Responsa for Yevamot 169:7
שניות מדברי סופרים וכו': בעו מיניה בני בירי מרב ששת שניה לבעל ולא שניה ליבם יש לה כתובה מיבם או לא כיון דאמר מר כתובתה על נכסי בעלה הראשון לית לה
Said R. Huna son of R. Joshua to him: Only cases where the women may marry the men, and the men may marry the women were enumerated;<span class="x" onmousemove="('comment',' Lit., 'wherever these take from those and those take from these he taught'. ');"><sup>20</sup></span> the case of the Priest, however,<span class="x" onmousemove="('comment',' Though, were he a halal, he would not have been forbidden to marry a priest's daughter. ');"><sup>21</sup></span> was not mentioned, because a halalah, should he even desire to marry one, is forbidden to him.<span class="x" onmousemove="('comment',' So that the Mishnah of Kid. is not conclusive. ');"><sup>22</sup></span> When they came before R. Idi b. Abin he said to them, 'O, school-children! Thus said Rab Judah in the name of Rab: Women of legitimate [priestly] status were not forbidden to be married to men of illegitimate Status'.<span class="x" onmousemove="('comment',' V. supra 84b. ');"><sup>23</sup></span>
Teshuvot Maharam
A. If L refuses to accept a divorce, Rabbi Eliezer is permitted to marry another woman. Rabbenu Gershom had intended that his prohibition against bigamy should apply only when the first marriage was legitimately contracted; but he had not intended to protect by his takkanah the marriage of a loose and immoral woman. Those who impute such intentions to Rabbenu Gershom will receive severe punishment from Heaven for defaming this saint's character and malignantly ascribing to him silly ordinances in order to make him appear ridiculous and thus discredit his other takkanot. Thus, the Rabbis are intent upon breaking up the marriage of a man to a woman pregnant by another. Would, then, Rabbenu Gershom protect such a marriage by his takkanah! I am even inclined to the opinion that the betrothal itself was invalid since the bridegroom was ignorant of facts, the knowledge of which would have prevented him from marrying L. There is no doubt, however, that Rabbi Eliezer is permitted to marry another woman in case L refuses to accept a divorce.
SOURCES: Cr. 161.