In reading the headlines about Bruce Jenner's recent announcement about his decision to "transition" from being a man to a woman, I got to thinking if Calvin had any advice for contemporary Christians about how to evaluate such a decision. To seek a perspective on this, I turned to Calvin's comments on Deuteronomy 22:5 which says, "A woman shall not wear man’s clothing, nor shall a man put on a woman’s clothing; for whoever does these things is an abomination to the Lord your God." On this text Calvin says,
This decree also commends modesty in general, and in it God anticipates the danger, lest women should harden themselves into forgetfulness of modesty, or men should degenerate into effeminacy unworthy of their nature. Garments are not in themselves of so much importance; but as it is disgraceful for men to become effeminate, and also for women to affect manliness in their dress and gestures, propriety and modesty are prescribed, not only for decency's sake, but lest one kind of liberty should at length lead to something worse. The words of the heathen poet are very true: 
"What shame can she, who wears a helmet, show, Her sex deserting?"
Wherefore, decency in the fashion of the clothes is an excellent preservative of modesty.
As you can see from these comments, Calvin thinks this ancient OT text has something to say to our modern situation regarding the idea of a man dressing like a woman, and beyond that, perhaps even to a man "transitioning" from one gender to another. Not only does Calvin argue that it is disgraceful for women to "affect manliness" either in gesture or dress, he also claims to find support for his view in an unnamed "heathen" poet who affirmed that it is shameful for a woman to dress like a man. Beyond applying this commandment to apparel, Calvin applies it to gender deportment, conduct, and demeanor as he argues that it is disgraceful for men "to become effiminate" as it is "unworthy of their nature" having been created by God as a men.
It is interesting to compare Calvin's comments on this text to older and newer commentaries. Some older commentators include Matthew Henry and Matthew Poole. Both agree that this text continues to have binding authority under the New Covenant. Poole here says, this is forbidden, partly for decency sake, that men might not confound, nor seem to confound, those sexes which God hath distinguished, that all appearance of evil might be avoided, such change of garments carrying a manifest umbrage or sign of softness and effeminacy in the man, of arrogance and impudency in the woman, of lightness and petulancy in both." Matthew Henry's comments are similar as he explains, "The distinction of sexes by the apparel is to be kept up, for the preservation of our own and our neighbour’s chastity." Obviously both of these Reformed commentators agree with Calvin's interpretation that this commandment is not just for the Old Covenant dispensation, since it states a moral principle which has binding validity on account of its being grounded in the creation order.
Interestingly, newer commentators (19th century) hold the same view. Keil and Delitzsch can be taken to stand for new commentators and they hold the same line found in Calvin as they expound the meaning of this text when they say, "the divine distinction of the sexes, which was kept sacred in civil life by the clothing peculiar to each sex, was to be not less but even more sacredly observed." What is more, they don't hesitate to venture into making a broader application of this text as they go on to explain, "The immediate design of this prohibition was not to prevent licentiousness, or to oppose idolatrous practices (the proofs which Spencer has adduced of the existence of such usages among heathen nations are very far-fetched); but to maintain the sanctity of that distinction of the sexes which was established by the creation of man and woman, and in relation to which Israel was not to sin. Every violation or wiping out of this distinction—such even, for example, as the emancipation of a woman—was unnatural, and therefore an abomination in the sight of God."
Our takeway from these brief observations about Deuteronomy 22:5, found in Calvin's comments upon this text and in other well-regarded Protestant commentators, is that historic Reformed interpretation of this commandment indicates it has an ongoing application under the New Covenant. More than that, Calvin and subsequent commentators such as Henry, Poole, and Keil and Delitzsch, argue that the prohibition against cross-dressing, is not rooted in a peculiar cultural situation, rather, the prohibition is rooted in the unchanging nature of God's ordering of creation.
It could be argued that it is open for discussion whether Deuteronomy 22:5 addresses the matter of gender reassignment surgery, but, based upon the interpretation and application of this command by Calvin and leading Reformed commentators, it does not appear that any doubt exists as to whether it addresses the subject of cross-dressing. While there may be some question regarding what precisely constitutes a man wearing a woman's clothes, there is no question about the principle which Deuteronomy 22:5 seeks to address which is that both men and women are under a sacred obligation to maintain and uphold gender distinctions in their clothing and external deportment.