Halacha Corner: Is it Permissible for a Man to Dress as a Woman?
Understanding the proper approach to cross-dressing for celebrations such as weddings and Purim

Question: Is there any permission for the practice in some communities where girls wear boys' clothing and boys wear girls' clothing, doing so for the joy of a mitzvah such as at weddings and during Purim, or is this prohibited?
Answer: The Torah states (Leviticus 19): "A man's item shall not be on a woman, and a man shall not wear a woman's garment," from which we learn that it is forbidden for a man to wear women's clothing, and likewise forbidden for a woman to wear men's clothing.
It is explained in the Shulchan Aruch Yoreh Deah (Section 156) that it is forbidden for a man to do something that is specifically for women's adornment, such as looking in a mirror, which was not customary for men but was a women's practice, and therefore forbidden for men. Nevertheless, the authorities wrote that in places where men also customarily look in mirrors, there is no concern of prohibition at all, since it is not exclusively a women's practice. Therefore, in our time, it is customary to be lenient and allow men to look in mirrors without concern for prohibition. However, wearing actual women's clothing is not permitted, as this is exclusively a women's adornment.
Nevertheless, in some Ashkenazi communities, it became customary for men to wear women's clothing and women to wear men's clothing during Purim. The Gaon Maharil Mintz wrote that the reason this was permitted was because during Purim everyone engaged in this practice, so during these days, these clothes were not exclusively for women or men alone, and therefore there was no prohibition, similar to the permission to look in mirrors nowadays. He further wrote that since this was not done for any sinful purpose, Heaven forbid, but for the joy of Purim, there is no prohibition. He provided reasoning for his position. The Rema wrote similarly in his gloss on the Shulchan Aruch.
Nevertheless, the opinion of most authorities, led by the Rambam, is that one should not be lenient regarding any prohibition, even for the joy of Purim. Consider what Rabbi Eliezer of Metz wrote in Sefer Yereim: "Even temporarily and in jest, it is forbidden for a man to wear women's clothing, and vice versa, as the Torah does not distinguish between temporary and permanent wear. I needed to write this because I saw people wearing women's clothing temporarily at wedding feasts." It is thus clear from his words that even for the joy of a mitzvah, one should not be lenient in this matter at all, as it involves a potential Torah prohibition.
This was also the conclusion of Rabbi Ovadia Yosef in his responsa Yechaveh Da'at, who cited many later authorities who wrote similarly and expressed strong opposition to those who are lenient in this matter. Rabbi Ovadia concluded: "These matters should be said gently so that they will be accepted." That is, these matters should be conveyed calmly so that the listeners will accept them.
It appears that adults are responsible for ensuring that children do not dress in clothing of the opposite gender, and vice versa, due to the mitzvah of education. As with all Torah commandments and rabbinic teachings, we are commanded to educate young children so they do not come to violate these prohibitions.
In summary: It is forbidden for girls or women to wear men's clothing, and likewise, it is forbidden for boys or men to wear women's clothing, even for the joy of a mitzvah. Those who heed our words will dwell securely.