Lex Lavacrum is my best effort to translate into Latin the words "Bathroom Law" or perhaps more appropriately "The Law of the Bathroom." What seems silly in English acquires a certain majesty when translated into Latin, however loosely. I confess that the idea of bathroom law as a kind of specialty practice has a certain appeal to me. I rejoice in the silly. But the fact is that someday soon there may be (if there are not already) courses, seminars, certifications in bathroom law thanks to the efforts of those who seek to regulate human excretion, or at least decree which humans may excrete in certain places. Public bathrooms and who may use them now consume us, or some of us, there being little else worthy of our concern it seems.
Lex Lavacrum, Lex Dei seems to be the premise on which the laws we see cropping up these days are based, ultimately. The law of the bathroom is the law of God, and God being concerned most of all with sex commands that only those with appropriate genitals may use public bathrooms. If you lack the proper genitals, you may not use bathrooms designated for men or women regardless of whether you consider yourself to be a man or woman. Regardless, in other words, of how you "identify" in the current usage of that word.
What, though, of those of us who identify as neither man nor woman? There are those who identify themselves as cats or dogs or other creatures, presumably. Will they demand the right to use our cats' litter boxes or squat on our lawns? What would God have to say about that? As noted, I rejoice in the silly. But this would be a species identity issue, not a gender identity one, and I think we may assume--for the time being at least--that species identity doesn't create legal issues applicable to the Lex Lavacrum.
To be fair (if it's possible to speak of fairness in bathroom law), divine command isn't the sole basis on which bathroom laws are adopted or urged. There are said to be privacy and safety concerns.
Now whether and to what extent privacy can reasonably be expected in a public bathroom presents an interesting question. Whether it should be a concern of the law presents an interesting question as well. Most men urinate brazenly standing next to other men with considerable frequency. A man demanding that he be allowed under the law to do so alone in a public bathroom for privacy reasons would probably not get far in court or in a legislature. But it's likely that the law would recognize that there are privacy concerns at issue in some circumstances.
I'm now at an age when my need to urinate is sometimes of such urgency that urinate I will even if surrounded by nuns or while standing alone in the middle of a crowded arena. But I admit that I'd feel somewhat uncomfortable doing so, though primarily relieved. But are privacy concerns in a public bathroom something which demands the adoption of a law to be enforced? Should the law protect us from embarrassment in these circumstances?
As to safety concerns, I have trouble understanding why they exist. If it's maintained that people who identify as women or men but lack the requisite genitalia are more likely to assault other people than are others, it's not unreasonable to demand that be established before a law is adopted, and as far as I know there's been no effort to establish that's the case. In the absence of any evidence to that effect, it would seem as likely that a man could enter a public bathroom and commit assault regardless of whether he identified as a man instead of a woman.
For my part, I see no need for such laws, and think laws should be adopted for good reason. As Cicero wrote, "The more laws, the less justice" (Summum ius, summa iniura--sounds even better, doesn't it?).
Of course, if the use of public bathrooms isn't such a concern as to demand adoption of special laws governing their use, then may it not also be claimed that the legal system should not be used to enforce the "right" of transgender people to use any particular bathroom? That doesn't work though. The use of the legal system in that case is to address a prohibition which already exists in the law. There should be good reason for the prohibition. If there is none, it should be subject to challenge.
It seems religion is the go-to basis for legal claims that people should or may be excluded from certain places or refused certain services these days. Ingeniously if disingenuously, the argument is made that it's discrimination to prevent discrimination if the discrimination is based on some sincerely held religious belief. But this is to maintain that the law should protect and sanction religious conduct and beliefs, though of course only of a particular kind. The Constitutional prohibition against adopting laws prohibiting the exercise of religion is, like all other Constitutional provisions (except the Second Amendment, according to some) subject to reasonable interpretation. If it's necessary to unreasonably limit the legal rights of others in order to exercise a religion, the exercise of that religion may be prohibited in that respect.
Regardless of these profound legal issues, though, Ciceronianus won't practice bathroom law if he can help it.