What the advocate of traditional ethical reasoning has to say about this matter will depend on what he or she believes about human nature and the goods that contribute to or constitute its flourishing. What is generally and unsurprisingly the case, however, is that most proponents of "natural law" reasoning take a socially conservative position. According to such reasoning, judgments as to the moral acceptability of sexual practices must be linked to an understanding of the proper role of sex in human life. Sexual activity is defined by function and its (primary) function is that of reproduction. What follows is that the definitive use of sexual organs is inter-sexual, i.e. between male and female, and for the sake of procreation. This is not to say, however, that the only function of sex or of the sexual organs is to reproduce. Sex obviously gives pleasure and serves to express and deepen emotional bonds as well as to effect an uniquely intimate union between distinct but complementary psychophysical natures; but these features are located within the framework of its primary, reproductive function. Something of this plurality is invoked by the philosopher Sir Anthony Kenny, who argued in his book What I Believe that homosexuality is a form of disability or handicap. 

Suppose, then, that a natural law theorist believes homosexual practice to be contrary to the proper role of sexuality, and thus at odds with right reason, what should follow so far as policy is concerned given the fact that this opinion is now widely contested? Here it may be useful to recall a real case in which, as with same-sex marriage, moral and political views on these issues have been in heated conflict. In 1988 the Conservative administration of Margaret Thatcher enacted local government legislation containing the following clause, known universally as Section 28:

A local authority shall not (a) intentionally promote homosexuality or publish material with the intention of promoting homosexuality; or (b) promote the teaching of homosexuality as a pretended family relationship. (Local Government Act, 1988, Section 28.)

This was introduced in legislation designed to curb what were represented as doctrinaire policies then being advanced, and sometimes implemented, by political activists particularly in London. The general legislation was contested by the parliamentary opposition, and the clause was viewed with some disquiet by others, but it was presented as part of a general restraint on policies for which the public appeared to have little if any sympathy. In fact, the dominant feeling, then as now, was probably one of wishing not to know what people do in private so long as it is not contrary to the well-being or interests of others.